I have a scratch built electric 3D flat foamy and I'm using the standard Futaba R127DF receiver on it. Would it be worth removing the receiver from the case for a weight savings? Would there be any real risks to the receiver on an electric plane such as this? If so, should the bare circuit board receiver be wrapped in bubble wrap or something? Would I see a noticeable difference in flight? The plane flys great as it is, but of course, I'm just trying to make it even better. Thanks.

You can...then just wrap it in heat shrink tubing....

or just spend a few bucks for a micro rX , use it in your foamy and put your normal in a bigger plane

I often remove the case, mostly for the tiny noses on some foamies and DLG-planes. Not much space...
If you want to wrap your RX in any kind of foam take care! Some foam and bubblewrap-plastics are anti-static, this can cause short-circuits to your RX. Especially some of the black bubblewrap but also pink/red types.
Do as exeter_acres says, buy a micro-RX. I`m very pleased with my Penta5`s, just 4 gram and 5 channels...