Slightly longer, I think scale works great for glancing blows and blows raining down in the direction of the scale, but you tend to lose a lot of protection from blows that come up against the direction of the scale. Chain doesn't have that problem.
In any case, chain is usually worn over quilted jerkins and the like which spreads the impact of blows. So, that "extra layer" that scale has, chain has too.
Well, thats what you've got your horse for. As long as being mounted I would ruel that most checks on fatigue are made by the horse. Given the stats of a horse in Mundane Beasts (download from atlas games) such a horse could go for quite some time before getting tired.
Anybody wealthy enough to by two full chain mail suits will also be able to afford an additional horse and someone waiting outside the battle to help you change mounts.
Double mail refered to the number of rings interlocked togther not to wearing two mail shirts. I am not sure if the number is acutally doubled since I think it only goes from 4 to 6 but don't quote me on that.
I won't say absolutely no one wore two mail coats one over the other but it was not anything I've ever read of as common.
Also mail is probably a hauburk while scale is a quasi breastplate so a higher protection value is reasonable. If mail is better protection depends largely on what you are being hit with. Scale mail is probably better protection against blunt weapons as the combination of metal plates over a somewhat stiff leather coat spreads the impact better than padding itself will (the mail does nothing to stop blunt force trauma), but the mail is signficicantly better at slashing damage as cutting through the links is nearly impossible, and the padding is there to absorb the force. Punctures are dependant on a lot of things but the descriptions of the army destroyed in the Holy Land in the battle of the horns of hattin (I doubt i have the name spelled properly) had the men-at-arms looking like pin cushions so I think its safe to assume that it could stop arrows from doing damage.
One thing to be clear about, you will be black and blue after a battle and you may have broken bones but you won't be cut apart.
The romans went from scale armor to chain armor over the course of the empire and before the quality of their infantry took a serious nose dive so I'm inclined to imagine it has got some advantages.
It is certainly less encumbering to be in chain then scale armour and the overall protection is likely higher taking into account the joints and so forth.
The weights of most games for armor bear passing little resemblance to the weight of the armour in reality. SCA armor is significantly heavier than anything normally worn at the time except late period jousting armor but that is not battlefield use intended.
At this period (1200) it would have been the show off thing to do to vault into your saddle during your knighting ceremony. This is a practical skill demonstration (though one that was not easy to do) as being unhorsed in combat would have been common. Knights were by no means neither able to get up, nor remount...if you were in tournament armour from the 1500's yes that might be the case but not in field plate of the time and certainly not in any armour available in 1220 (reinforced chain hauburk and trues, plate and chain or else the start of true plate armor I'm not sure which is more likely my memory is not exact and I don't feel like looking it up on the wikipedia).
Having seen plate from the 1500's at Ingolstad's armory there is no obvious reason for it to be either particulary encumbering or that heavy and a mail shirt (not a hauburk) on display at the Deutsches Museum was clearly not very heavy.
Full chain would include leggings, gloves/gauntlets, a coif(sp) and a helmet in addition to the hauberk. It would also have padding under all of these pieces.
Remembering battlefield descriptions, anyone equiped with this would be pretty invulnerable to most weapons, so that an attacker would need to find a weak spot (like under the helmet from the front) to kill him. An army equipped like this would be formidable indeed...
As for the weight, I've never tried SCA armour, but I have tried a period mail hauberk. It does weight abit, which does limit ones running speed, but not by much for a short engagement. And certainly most knights would be in far better shape than me;)
Oh, and it does help a little against blunt truma, but since people never tried to kill me while I wore it (just make me notice that I had been hit), I really can't say how much....
I've always been terrible to watch TV with because of my stickler nature with weapons and armour realism. The new Robin Hood (BBC i think) is the worst offender i have ever seen.
The number of times a chainmail armoured guardsman gets slashed across the belly and instantly falls down dead is huge. The Sheriff of Nottingham should clearly fire his armourer. As PaulM said in his rather-good-indeed post, chainmail makes you all but immune to slashing attacks. Piercing and bludgeoning not so much.
The other one that really bugs me is Robin shooting his best friend, at point blank range, with a longbow to convince the sheriff he really is dangerous. His friend of course was well protected. He had a wooden tray under his shirt. At that kind of range an arrow fired from a longbow would go through plate armour, not to mention wooden trays.
As for scale being better than chain, not really but it certainly looks cooler. And because of the small metal scales can actually be "shined up" quite nicely. This perhaps would be a good reason for senior soldiers to wear it rather than front line troops. It makes them more noticeable and impressive and thats good for morale and control.
Could the lower protection values from scale mail be explained by the relative ease with which limbs and joints could be covered with chain without having to compromise the design of the armor? Can scale be "draped" the way chain is?