Spell Design with "General" Level Spells

I'm very much looking forward to my first AM campaign, but I had one question come up during character creation that keeps bothering me. I went through my due diligence in trying to find an answer in FAQs and on this board, but didn't come up with anything.

I understand how "General" level spells are created at a set level, depending on how strong a magus wishes to (or can) make it. If a different level of that spell is desired, it must be created separately.

My question is, can "General" spells have their base range/duration/target adjusted, as with other spells? The way I'm reading it, r/d/t can each be increased a step on their respective scales for a 5 level (1 magnitude) boost. Since "General" spells don't have a base level, though, I'm not sure what can be done with them.

Any insight would be appreciated- thanks!

Yes R/D/T can be changed. General spells have the base level that you select each one of them to have.

So let's say I want to create a spell using Ring of Warding Against Spirits (ReMe) as a base, but I'd like to boost the Duration from Ring to Moon.

Arbitrarily I've decided to have a base effect of 10 levels. Then I add on the 5 levels for the increase to the spell's Duration, for a total of 15. Doesn't that extra 5 levels count for the spell's effect (keeping out spirits with a Might lower than the spell's level), though?

In other words, with a spell like this, if I choose to have a level of 25, do I get 5 "free" R/D/T increases?

I'm sure I'm just missing a fundamental point, so I greatly appreciate the help.

Short answer: no.

The increases in magnitude for changing the range, duration or target of the spell does not change the base effect. Just as Sight range Pilum of Fire does not do more damage simply because it has Sight range, a Moon duration ward does not ward against more powerful beings.

Ahh...so with General spells, the base level is what determines the power of the spell, not the overall level of the spell?

This is true of all spells. The difference between General and other spells is that general spells have a base level of whatever level you want the base level to be. Think of them as any other spell but having a base level 5, base level 10, base level 23, etc, version.

Aha! I see. I was getting tripped up by the difference between the base level and the overall level.

Thank you to everyone who contributed their help!