ok so this is the thing that did the job...!
I spread it with a brush on both surfaces. It has been a week+ and it seems rock solid.
Since i glued the linings nearly 4 times so far.....
, on my last try i decided to stick another layer of insulation, 1cm contracted in all sides so i have a nice fade. Now there is a 10cm thick insulation.
I believe this time i did it.