Hey man, 46AX is definetely not the engine for that plane..... you need to gain lots of speed with that engine for a decent take off and you will need LOTS (seriously, lots!)of weight at the front to balance it.... I strongly encourage you not to out that engine.... I would put AT LEAST an OS 55AX and not even. I would go for a 4-stroke 70 or 82.... that plane is big and heavy, it needs good power and if you are going to put extra weight, better to be with a bigger engine..... I think the OS 61 is a good choice too...
just my opinion....

P.S. The plane is beautiful....