I've used this on my Slope Monkey wing. It stick great to balsa, but not so much on EPP. There are lots of air pockets where it didn't bond. I was working from the middle outwards FWIW.

The instructions I first read were to keep the temp at 220°, but I found this didn't melt the adhesive backing adequately. 300° worked better.

Could it possibly too hot and affect the EPP itself preventing a good bond?

I thought I read once somebody used 3M77 on the EPP first and then applied the New Stuff...but can't find where I read it. Would this be a realistic technique?