I am also building the CMP Cessna 152. I plan on installing the Spektrum DS821 servos that come with the Spektrum DX7 7CH DMS2 System MD2 w/AR7000 RX. It come with 4 DS821 and I am installing 3 more of options. The servos are plenty strong enough at 72 oz/in. I have been reading up on the Radios (Spektrum and Futaba) and most problems people are having come from the Batteries running low. Try and find input on the DX6i. I think you will be fine using that radio. Keep the batteries charged up.