I had the EXACT same problem with my GP US40+. I releived the aft-most edge of the opening with a round file, that helped some, but much to my surprise, the friction all but vanished when I pulled the aft ends of the pushrods out from the fuse 1/16" or so. I plan to install the elevator cortrol horns so that they hold the rods away from the fuse like this. Almost no lateral pressure is required to accomplish this and the change in resistance on the control rod is amazing. Being a newbie I was in a panic about this untill I showed it to a very experienced modeler - he showed me the light!