How to bend core

How do you put a bow in core material when building a hard top? I'm going to use 1 1/4 inch thick 5lb divinicell or similar foam core and have a slight bow to the top. The natural sag of the material may be enough, but if not can you heat it with a heat gun or something similar to get it to lay on the mold? I'm sure that vacuum would do it, but I don't have a vacuum pump and may try to suck it down with a shop vac. I don't want to have to relie on that to get the foam to pull down, or am I worrying about nothing. The top is 8 ft wide and has a 2 to 3 inch bow in it.

 

Don't know about divinycell but I've seen core-cell heated to form to a mold as well as screwed to the mold from either side to hold the shape. A vaccum press on a part that size would be a challenge. I've seen it done this way too.



I believe there were sandbags hanging from those loops.