Here's what I do. Cut the canopy from the base, make centerline marks on the front deck, windscreen bar, canopy front frame bow and aft frame bow, along with corresponding marks on the canopy. Trim to the line already marked on the canopy, keep trimming the front until the canopy comes down onto the frame at the windscreen. Trim the sides enough to get a couple of clamps on the sides, don't worry about the rear yet. Tape the front of the canopy to the front deck and put one clamp at the very aft. MAKE THE BIG CUT! Now set the windscreen aside, and remove the frame and put it on the bench. Put the canopy back on the frame and put one clamp at the front bow at the top center, then begin clamping from the REAR and work your way forward. This relieves all the pressure you guys are getting by allowing the canopy bottom forward edge to "grow" forward of canopy front bow. I just re-trim this edge. The fiberglass "targa" strip will cover any gap later. I have found this method then allows the pink canopy skins to fit almost perfectly.
A tip for the skins- Drill and cleco the skins to the frame except for the tails. Then get a helper to pull the tails around the aft end of the canopy while also exerting some forward/upward pressure on the "tail". This pressure causes the skin to "suck" into the fuselage just after the rear seat bulkhead. Drill the "blind" holes while your helper keeps the pressure on. The skins overlap and will require retrimming of the "notch" for the rail, and then will have to be spliced or joined per builder choice.