Ghosts of Magi?

I'm trying to create the ghost of a long-dead but very powerful magus; I have a couple of questions.

First of all, how would you go about calculating such a ghost's might score? The other ghosts I can find stats for seem to have fairly arbitrary might scores, but it seems like there should be a method for deriving a specific value from something like a magus that has a lot of stats to work with.

Second; can you use an object with a spirit bound to it to create a talisman? (I'm referring here to RoP:tI p. 117)

Third; if you summoned the spirit of a magus and his body was still intact, would both the spirit and the body be magical? I.e, where does the Gift 'live'? In your soul or in your body?

In Rival Magic the ghosts of Amazon sorceresses have a might equal to their highest art (but the sample one in the book has a slightly higher might as they took the "improved might" quality a few times). So, as a rule of thumb use highest art then add or subtract a few points according to taste.

If the ghost was created by "The Living Ghost" mystery from The Mysteries then use their formula - highest Technique+form, double one if they have a focus in ghosts or self-transformation or death, then subtract the size of their haunt (50 for a boundary)

I seem to recall that RoP:M explicitly gives that as a rule of thumb for "transformed" beings.

Thanks guys! My troupe doesn't have access to either of those, but that little bit is precisely what I need to get me going down the right direction.