Bax, do you have a bit more about this. Simply getting the right area isn't the whole thing to get adequate pitch control/authority.

A guy at the field today flew a new design that was pretty badly unstable. It had the appropriate area for the tail. Both stab/elevator and fin/rudder were adequate for sure. But both were almost slap up against the wing. He got about 50' on the first flight. The corn saved it. The 2nd and 3rd flights went about 50' each. He took it home in a bag.

You need something that helps establish the stab/elevator that takes into considertaion how far back to place it.

BTW, full scale designers also take into consideration where the horizontal tail is in relationship to the wing's downwash. The up-down location of the tail and it's resulting performance because of that location really does influence how the plane performs.

This stuff actually ain't simple.