For anyone that is looking to upgrade to these servos, before you go on the wild goose chase that I went on looking for a screw, here is the size. 2-64. For the RC18, I got the 3/8" long one. I drove to many hobby shops, bought the Hitec screw set figuring that it should work(wrong), and finally ended up at a large industrial supply shop. If you are in the San Diego area, I got it at Marshalls in Miramar. Good luck.

Thanks for this. I ended up re-tapping mine to a different size, but this will maybe help some guys looking to upgrade.

No problem, thats why i posted it up.