Thanks for all the advise... I'm going to check out what's up in the warbirds forum with this. The P-51 is a Black Horse which I mentioned in the original post. I will be trying the two elevator servors together. That will leave me with 3 channels for flaps AND ailerons. I've run into this problem before on a 4 channel and 2 servos on the tail, y-ing them was just fine. I had to take few runs to get them to be sync'd 100% but they were OK on the maiden.

BTW, Black Horse's instructions suck moose balls, but the quality of the builds are really good. FWIW!