According to :

How to cut it??/ I used a miter saw with the blade backwards.
You do not want to cut the material you want to grind it away for
clean cuts. You can also use a sharp blade or scissors to cut it.

Aviation tinsnips work quite well. They have the leverage to
cut cleanly and accurately under control without requiring too much
grunting, cursing and swearing, and less likely to draw blood than
a knife ;-)

Not remotely as fast as a mitre saw, and you'll want to avoid
exposing many of your end cuts. But for a first-timer, it paces
things out nicely, and you don't have to get so crazy about safety
gear.

Did a 14'x14' gable end shed (9' side walls). First time with
vinyl. Two relaxing days of work. A pro with a mitre saw could
have probably done it by lunch break on the first day.

S'alright. It was a nice weekend.

Result really nice if I do say so myself.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.