I started with mine at about 5 1/4" from the leading edge. Powered with a YS91FZ and the tank on the CG. Hovers and spins/snaps are easier when it was moved back to 6 1/4". However, the coupling in knife edge was horrendous. I've since moved it forward again to about 5 3/4". Knife edge takes only a little mixing (unless you are at a high deflection) and hovering and snaps are manageable (a little harder). Landing is more on the main gear at this setting (easier in high wind)

Chris