I no longer have mine (sold it) but I flew one for a long time with a Saito .65 four stroker.  It was enough but certainly not too much.  The .72 would be a better choice and an .80 or .90 would be even better, IMHO.  They are great flyers and the only hard part is getting them down without bouncing.  At least that was the only issue I ever had with it.