Pasting the cloth method.
After my poor initial adhesion, my test results weren't impressive either. Even with the dimpling, and overnight, adhesion wasn't impressive. How to correct and assess.
So I lifted the canvas on the wall that I had already done about 12" from the edge and stoked more glue full strength. Theory being that the edges will lift and be a problem first. The inner could probably get away with less.
Hopefully. Maybe. You know what to do.
Dimpling showed no benefit whatsoever and if anything, was negative, with a hole not being properly filled and adhered to. Didn't dimple at all except for an initial small section on one wall. Besides, my cheap dollar store massager, which I used for a dimpler, broke and wasn't going to stand up to the rigors of the job. Chuck that idea.
It was only an instrument for more cussing.
I finally decided, based on a guess, that 80/20 TB3/ water is what I would use. Sounds about right, right?
Hopefully, maybe, you know what to do...
Mix it up and slap it on all over, sounds like a sex tape, but I digress.
Paint the TB3 on with a 4" brush, need to work it into the Polystyrene which isn't smooth like polyiso. Do like George said, do a 12-15" by full length 7' section of glue on, first the foam, spray the cloth with water, brush the glue into the cloth section, unfold and smooth onto the foam. George uses a roller which works for him. Initially I used a 12" wide plaster mud spreader which was ok but tended to pull or catch the cloth and sometimes distort the alignment of the weave. Found that, wearing the cheap rubber faced gloves, would just flatten and smooth with my hands, would work well initially, then go back over it with a 4-5" plastic putty spreader to ensure good adhesion contact by pulling the spreader over the cloth surface. Hands on, enjoyed this part. No cussing involved. Until the next day.
If you pulled the cloth too much while laying or trying to straighten the seams, that while drying, could contract and revert to it's original, uneven lay. So it's important not to stretch the fabric too much when laying and pasting as well as ensuring that it's straight and aligned before you start. If you have to pull too much, it will distort the fabric and give uneven results. The fabric weave will be pulled and crooked. And the seams which are seen will show as crooked and obvious.
This can be dealt with by cutting out the seams, lots of paint to hide the weave and that will minimize the problem.
Make it so.