Hi there,
The VMAR Edge is a heavy weight but a great flier.I'd put as much power under the hood as you can fit. It does well with the 70 4S.A bit slow but does well with the type of flying I do.I'd go with the two stroke 45 and see what happens.Turns more R's and will be a little faster.I'd question the 52 4S.It may work but may be a bit small for this plane due to the weight.
Put the engine at a 90 degrees (sideways).It works well that way and the muffler will be underneath.

If you want to try both engines try the one first that will take less cutting of the cowl.

I have numerous flights on this plane and really like it.Altho there was a lot of bad press the plane flys well.The only problem is that the covering does not like hot sun.It'll bubble everywhere if it sits in the hot sun.

Have fun
Walt