If you are planning a DIY panel, it's a good idea to research the materials that you need to get the job done right.
The first thing that comes to mind is the EVA that is needed for lamination.
If your supplier cant give you a detailed list of the product composition, the Cure Type, (fast or slow cure or somewhere in between), the product shelf life, and the date of when the EVA was produced, it may save you some time and money to find a more reputable supplier.
The better the supplier, the more detailed the info will be.
I've purchased batches of EVA that came with Product Information Documentation that included optimum temperature ranges and time frames for proper adhesion.
Just like most anything else, buying in bulk should give you a discount.