4Ch is doable with a foamy but for larger aircraft set up with 3D throws it's pretty tough to fly well with no dual rates, and most also use expo (exponential) and these features aren't found on 4 channels. This is because you need tons of surface travel to 3D, and this is pretty hard to set up while still having a controllable plane. You will probably have to compromise the 3D throws somewhat to enable yourself to fly the model smoothly. I have flown the shockflyer types without issue using the basic 4ch though. My Funtana set up for 3D on high rates is terrible to fly if left on high rates (I have no expo on my current set up either) you can hardly move the sticks out of the center detents without a 400 degree/second roll. . . if I set this plane up without DR or expo I would have to savrifice the 3D capability by a large margin. There are some very cost effective radios out there with D/R and expo now though.

As far as servos, in a foamy that uses an electronic speed control to manage the throttle, you will need 3 - 4 servos depending on if you have a single aileron servo, or two. Even if you use two you can still use a 4ch with a splitter leading from the receiver to the two aileron servos.