The only problem I have had in mounting something on my Rover, is mounting the cycling computer. the dealer had installed it on the left handgrip, to the inside, and my hand would rest against while I was riding which I found very annoying. It was also difficult to see since it was to the left side of the left handbrake.
I decided that the best place for it was on the right side of the left steering arm, which would put it more towards the center of the trike, and it wouldn't be in the way of anything there, plus I would have my entire left hand grip back again. I removed the plug, on the right side of the left steering handle, and got a piece of 3/4 inch wooden dowel at home depot for a couple of dollars. I cut off about a 4 1/2 inch piece, but you could make it any length you want. I then glued it in the handlebar, where the plug was removed. It goes in about 2 inches, so it is nice and solid, which leaves about 2 1/2 inches sticking out which is plenty of room to mount any cycling computer or GPS.