M South,
You got some great suggestions here. I think the one from W8YE is the best.
It is simple to build and should be very strong. DO USE OAK or MAPLE.
You will be putting lots of stress on these, keep safety in mind.
I would look for a way to make sure the engine cannot go forward it he hold downs loosen up.
The one I built is much more elaborate, but I really enjoy woodworking.
I also included its own receiver and servo for throttle control.
I used old stuff to here to keep the cost down. It sure makes tuning a lot easier with that precise control.
Good luck and have fun,
KW_Counter