I have my WM 80" Extra ready to fly. I put triangle stock on both sides of all bulkheads and tied the engine box into the landing gear plate. Have 3 batteries in it,epoxied the tail on, used Robart hinges, and Rocket City horns. Otherwise it is built stock.The best part is that it balanced right on the money first time! For an engine I used a BME 44 with a JA pitts muffler. There was plenty of clearance for a 20" prop. Unlike another poster the supplied pilot fit in mine.

Specs for my completed plane:
span 80.5", area 1175, weight 16.01 lbs

Specs for similar sized ARF's by manufacturers:
WM Extra: span 80.5", area 1175, weight 14 lbs
Horizon Cap: span 80", area not listed, weight 14-16 lbs
Lanier Cap: span 80", area 1265, weight 12-17 lbs
GP Extra: span 78", area 1157, weight 14-16 lbs

Looking at the above I think it should fly just fine.