Got a reply to my email about using the foam, kind of the answer I expected. Here's what he said:
My video is the best explanation.
Yes the expanding foam will blow things apart if you try to use it in a sealed area, which would be remarkably foolish!
Please watch my video as there is so much more to it. You'll find your answers there.
Note that you must use the "2lb" foam and NOT "6lb"
Scott Meyers
Reckless Adventurer and General Bum
M5 Performance Hydroplanes
https://youtube.com/user/matinco2
https://m.facebook.com/M5-Performanc...?ref=bookmarks
I don't have a Facebook account so I couldn't open the video so I don't know what it shows
HJ