19.5 ft x 42% = 98.25" Your going to need a bigger engine or a smaller airplane. :-)

The 42% racers that I saw were being flown with 4.4 c.i. (75cc) A3, Husky or Aerrow gas engines, but I guess the Zenoah 445s on glow are the dominant F1 engine these days.

I found this with a little searching. This might suit your engine choice.

http://www.hacker-model.cz/news/tony.htm

Strega