6 point FBT user here

Would it be possible to have an option to measure avatar by both height and arm length? To allow both arms and legs to match up better?

Or perhaps have an option to adjust arm length while using measure avatar by height.

I like how measuring by height allows us to matchup the floor and legs better but having the arms match up is vital as well, has over/under stretching can occur while using measure avatar by height, depending on the avatar. In general, I find that using measure avatar by height makes the arms feel less accurate.

Using measure avatar by arm length makes the arms more accurate, but then floor and legs don't match up.

I'm not sure if getting 10 point tracking will help this.