I built an enclosure years ago with a very thick cardboard tube. ( my brother worked at a paper mill ) The tube was 3/4 inch thick ( used as a shipping container for the $50,000 felt for the machine. No delamination at all. Nothing to worry about.
FYI, polyester bodyfiller works good to level off the surface after the resin. A long board sander will help you level it all off. A few passes with P180 paper and you will be ready for primer. You may want to use a notched glue spreader trowel to put on a thicker first pass, then when that cures a smooth spreader to give you a nice thicker coat to sand smooth.
"You take the blue pill - the story ends, you wake up in your bed and believe whatever you want to believe. You take the red pill - you stay in Wonderland and I show you how deep the rabbit-hole goes."