I'm noticing the proportions of the IPI skeleton and actor(me) don't match up perfectly.
Is IPI scaling bones to match what it sees when refitting pose or just approximating?
Perhaps having the ability to scale the bones manually aswell would help get more accurate tracking?

I'm not completely sure but I think Analyze Actor is also making adjustments to the rig...it seems to fit me, but I'll be doing tests with another performer soon who is the same height as me but has longer legs, so I'll know then.

Just to be sure, you do have a T-Pose to match to right? Also, when adjusting to the T-Pose you may need to alternate between Refit Pose and Analyze Actor several times (as recommended in their video,) to get a good 'fit' for the tracker. (I've found this to be a key step in getting a good track.) Recently, they've been suggesting setting the actor height slightly shorter (I haven't tried this yet.)

G.

Longer. Not shorter! :)
E.g. if actual height of actor is 1.80 m, then it is reasonable to perform experiments with height in range from 1.80 to 1.90.

My mistake! Thanks for correcting. :)