Thanks for the advice.
There would be no problem with landing gear or tank or any other foreseeable issues.
For some reason i just couldnt get my head around what the consequenes would be by doing this.
Lots of people seem to move it to suit the engine.
I will trace it out and see , it think i may need to make a new one slightly larger if i move back as the nose is tapered slightly to the front.
I will just need to shorten the fuse ply sides to suit.

I think i just worked it out in my little head, tell me if im wrong.
With the firewall back say 1/2" from normal then to keep the same thrust LINES i would need to mount the motor slightly HIGHER and slightly more LEFT than if it were in the plans position?

Steve