I tried to use the Dubro four stroke linkage on my Astro Hog but the cheeks were so close to the engine mount that I could not make it work. The engine is an OS 70 Surpass I with the metal throttle arm. With the carb turned so the linkage was opposite the muffler, the needle was hard to reach without getting burned, and with it turned the other way the throttle arm was directly behind the cylinder. I left it with the needle opposite the muffler; shortened the threads on a pushrod, shortened the nylon socket on one of these http://www3.towerhobbies.com/cgi-bin...?&I=LXD900&P=0 , and it worked pretty well. The brass part was not used.

If the throttle arm is not behind the cylinder, bending a "U" in a pushrod and using a standard nylon clevis usually works pretty well.