What have you been trying, to bust thru this imaginery wall, other than just getting fustrated. Have you checked your grip, have you tryed to hold a bit more line in the air. Perhaps your throwing too hard thinking that is whats called for to throw a longer line. Have you gone back to the basics in an effort to find were your over looking some small piece of the puzzle that isnt working for you. Personaly I dont think your going to find the answer at 60 ft; its more likely your going to find the answer at between 25 and 40ft. I say that because thats were your less likely to be intimadated and thus more relaxed and able to concentrate on the small details. Its easier to work on loop control, experiment with timeing an gain better feel of the double haul. Without ever haveing seen or spoken to you, I bet you added the double haul without makeing much change to your rod speed, loop design, or general over all stroke pattern. Thoes little details are were walls come from. Which arent walls at all but reather more like post-it notes reminding you that the way forward maybe to back up and get a better perspective on the road ahead.
Capt. Paul Darby Dont wait to be ask, get out and teach.