I think they are all the same servo! I have been using the same Hitec HS-5645's for two years now. No slop. I bought the DL-50 brand new fron Bob at DLUSA. It has never been run but I always put them on a test stand for some run-in time first and a chance to make friends with my new engine before putting it in the plane. I agree with JNorton on the 5645's. Exact same guts as the 5625 just different gear ratios. Good model "hygiene" will resolve a lot of slop issues that may not be related to your servos. Linkages and vibration woes need constant attention on any gasser!