I've been trying to get the retracts in my 60 size H9 P-51 to work. I have a hitec low profile HS-77BB servo in the wing but its like it just doesn't have the jam to lift the gear. I've played with it forever. Is the servo the problem or are these things just that hard to setup?

Is your battery fully charged? Low battery will make em run slow or not at all. Maybe you need a more powerful battery? What kind of servo arm are you using? The one that came with the servo? Can be another problem. Just food for thought.
Nearly my entire fleet consists of retracts. One other goodie is the type of wire used for the retracts. The cheap crap that comes with it can "Bow" out when pressure is applied. I replaced all mine with a 4-40 rod.

I missed the servo your using, the 77bb is not a retract servo and willnot properly work. Get the 75bb

You need a retract servo. For Hitec that would be an HS-75BB. The HS-77BB is not for retracts.

Thanks for the tips. I had a old set of Pneumatic Spring Airs sitting around, they'll be going in it tomorrow.