RE: what can i use to cut this foam?? (pic)
Glass has no give the blade meets the glass and does the job without getting misdirected. If you cut on a soft surface the blade gets misdirected. Try it, get a small piece of glass and make some cuts, you will see for yourself.
I have the luxury of having an AMA hall of fame-er in my club. Vertical ts's uncle, who has been on several AMA mag covers. He is a premiere builder and will have a more defined answer as to why. I picked it up from him 20 years ago. It's good for cutting covering material, balsa, foam just about everything.
Good luck
Whack