Here is a thread with someone who put a 38 in his Cub. I think he sold it though. Might want to ask him. Hope this helps
http://www.rcuniverse.com/forum/m_63.../tm.htm#636877
Lee
PS Mine has a G23 in the nose and it is very nose heavy. I think I put about 9 - 12 oz in the tail to balance. It does fly great though.