Dude; just move the cowl forward a bit.

Lots of us have used 120 four strokes without moving the firewall, putting the battery in the tail, etc. This is a pretty straight-forwrd kit to build, as are most CG products.

You are over-complicating a relatively easy-to-build model.

I understand and applaud your desire to get everything just so, but I also think you are causing yourself a lot of unnecessary angst here. Unless there are issues with your particular kit, or you aren't telling us something, if you just build the thing per the instructions, with perhaps a simple mod or two such as separate aileron servos, you will end up with a great model.

Steve