Try a 6" spackle knife for cutting foam.
Lightly and repeatedly drag a knife at about a 30 degree angle along a scribe line. Do not rush or pressure it. Repeat five or six times for 2" material. You will find a sweet spot which is the angle you need to use. The finished edge will be smooth with out making any smoke, crumbs or dust.
Note my scribe line. I set the curved module on top of the foam. Traced the bottom edge of the module with the corner of the spackle knife sliding it along the frame's lower edge then removed the module and went to work.
If foam builds up in front of knife, stop, clean out the plowed crud and continue at a shallower angle.
Work in progress for the late Pennsy K-4's module.