Not an RV expert.
I'm sure others will chime in with specifics as what i'm about to mention is not RV specific.
Cutting a canopy is one of those "critical" items in my book. When we did mine at the Lancair build assist, it was probably only 70ish degrees. Temp will play a part tho and I'd wait till you can get it warmed up or for a warm day.
We used one of those roto tools with a bit made for the task. It won't chip the plexi. Chips are what then lead to cracks.
I would expect that the scribe lines are just "best guesses". There must be specific alignment instructions in the manual that tell you how to position the canopy and mark it for your specific airplane? At least in my Lancair, no two are the same, so you have to transfer lines back and forth from the fuselage to canopy and vise-a-versa until you have all the right lines to cut.
Lastly, with mine, i also used a 1" belt sander, after it was cut, to take any remaining roto tool marks out of the edge.
Course on a glass airplane, there's lots more after that part, but it won't be applicable to a metal airplane.
So, probably not much help, but someone will know....
Alan