I agree with a couple of ratchet straps front to back. I haven't hauled a golf cart, but have towed a tractor on a utility trailer. The tractor had a fiberglass top that was only attached at the rear to the roll bar and just cantilevered over the front. But two ratchet straps attached to the steering wheel, run up and over the front of the top (one each side), and down the back and secured to the frame of the tractor and the top would ride fine at highway speeds. Since a golf cart top is attached at the front and rear it should be even more secure. Can't comment on the solar panels.
