Figuring the tail volume is pretty easy. I just ran down to the shop and measured the KYOSHO CALMATO SPORT I'm assembling. How long did that take? 3 minutes?

The h.tail is 143 sq.ins area, and the wing has a 10.8" chord and 659 sq.ins area. The tail arm is 32".

(143/659) X (32/10.8) =
(.217) x (2.96) = .642

You usually want to have something between .5 and .8 for your design.

BTW, the Calmato Sport is an almost perfect copy of the Tiger2 design.