I have a an FM Tx that works fine. The LHS will exchange the engine and let me make up the cost difference for a 55 AX or similar. They are pushing the OS 55 AX, but also sell tigre engines that are alot cheaper. Thanks for the info, I will wait on switching to 2.4. Though Hitec already had a 2.4 version. I was looking at the Futaba. THanks again for the input. could by both the engine and 2.4, but property tax is due and need a new heat pump for the house (Ouch!!).