Any 2.4 will do fine. Some have gone the route of trying to reduce weight and have gone with the FPE and use carbon fiber landing gear. I have one with a Fox 2.4 and it pulls very hard with a Pro Zinger 20x8 at 7700rpm.

P.S. don't listen to commentsa about gas being wrong for this plane, Sig reccomends a 2.4 and it does just fine.

Vince