Hi Brian, I believe Joe is correct, the reference I gave calculates the MAC and you can easily figure out where to put the cg based entirely on percentage of the MAC, if you don't want to consider the stab. In fact that is what I did as I didn't have a feel for the stab efficiency. I believe I also used your reference and got the same MAC so I figured they both had it right.

I also found moving the cg had little effect on the trim, until I got in the right ballpark. I was way nose heavy with the battery as far back as I could get it, and yes it flew like it was very heavy. I started thinking it didn't have enough wing area, but it turns out it does.

I suspect we can go more than 30% before we would get in trouble, but I am down to no rudder to elevator mix and no throttle to elevator on up lines so I'm pretty happy. I'd like to get rid of the rudder to aileron mix on knife edge and I still suspect vertical cg is part of the problem. However, Chip says all Axiomes need this mix. Do you guys agree?

Jim O