Sitting Too High @ The Aft End
If you mean the canopy hits the tubular frame before contacting the turtleneck skin - hence the canopy won't go any lower for the install, that is a problem that is not unusual given the vagaries of the RV-4 canopy frame production.
Not unusual to cut the bow right at the trailing edge, draw it together the necessary amount, re-weld it and build on.
I'm not sure I've seen it before on -4's, but I do know of -3's that have completely removed the aft portion of the bow to solve your problem.
I have seen -4's with partial removal (without the re-weld at the back) of the tube, and the amount of removed material was kind of all over the board - some go almost to the tail, others more (some much more) forward. They all seem to work - kind of up to you as to what you feel comfortable with?
YMMV - And probably will!
RV4 S/N 1136 Built, Flying, Sold