RE: Spad XIII
That sounds like a HUGE engine for a 63" 9lbs WWI biplane! I would imagine that even the RCV 90 would be more than enough.
BTW, the Dec. 2005 (Vol. 8, No.73) of Flying Scale Models has a Spad on the cover and a construction article on a 1/6 scale Spad XIII for electric (Peter Rake design). It's a good looking sport scale model.
The issue also includes a "history" article and two pages of color profiles. And of course the modeling tips and inspirations in ANY issue of FSM is worth the cover price alone.