Well I finally went with the Eflite Power 60 electric motor and managed to get the cowl distance right by reversing the front on the engine mount. I had to elongate the slots slightly to get the E60 far enough back and then I put four extra bolts at the rear of the slot to make sure it was really solid. This gave me a nice platform to mount the sound system. You can see from the picture I put the 4inch speaker on the engine mount held on with two 90degree plastic mounts taken from an old cut up cassette box. The speaker just fitted in nicely and missed the cowl. The ESC is on top of the mount with the speaker system amplifier and control electronics mounted in a receiver box held on the other side of the speaker. I may put the receiver batter on top of this (2 cell Lipo) if I need to get the CG further forward. At the moment the receiver (2.4GHz) and BEC are behind the firewall. I will carry on building but thought you might like to see initial efforts. Thanks again for the advice.