I use 2" up from center for arrow placement (and 2" down from that for a 4" handle) for a low wrist/full hand grip. For a medium grip I measure up 1 1/2" for arrow placement (and down 2 1/2" from that for a 4" handle). For a light touch or straight wrist I use 1-1 1/4" up from center for that. For me at least, this balances the dynamic forces very well.
I will say this, the lighter the touch (grip) you use on these selfbows, the better balanced they are, quicker, more quiet and better behaved than using a hard heel into the bow IMO. Better tiller health over time also. Best compremise for most of us is a medium grip I suppose. Have fun! ART