There are multiple solutions. I routed it out and put in an engine mounting plate for a Hyde A mount. Alot of work, but it came out real clean. There's quite a long Icepoint discussion thread starting at

http://www.rcuniverse.com/forum/m_22..._1/key_/tm.htm

Worth a look for different solutions to this and other questions, like, say, how about the hatch mount? Saw some good ways to handle that too.