u know putting a .91 in the SIG Something Extra is really pointless when it can hover adn 3d with an os 70 surpass... Here are some engines that will make your plane do 3d, ys 45 (pressurized fuel pump), rossi 45 (though heavy), webra 50, now for 4 strokes i would go with 2 engines, either the saito .56 or .72 or the ys .63. Any of these engines will make this plane hover! or do any manuever this plane is capable of... my 2 cents and if you want some cheaper engine, a TT .46 pro with a tuned macs pipe or a Super Tigre 50...