I don't see why the hot glue melting is a problem?? It is just a temporary way to hold the paper in place so that you can resin and fiberglass it. When you are done there is going to be so much resin, fiberglass and bondo holding everything together the hotglue isn't even a thought imo. I did have one piece warp, but I'm pretty sure was from the rondo heating up and not the glue. I could be wrong.
for Pepakura paper work yeah hot glue low temp works. But in this case they are building Foam armor.
My Wife Ashuraa and I have gone the Hot Glue route in the beginning. Okay here is a bit of a break down. Low Temp glue has a low enough melting point that your body heat from wearing it on a hot day is enough to start wanting it to soften. Not melt soften which weakens the joints out and will encourage high stress joints to want to pop. Leaving it in your car in say a california sunny day will be enough to melt low temp hot glue. Guess what fun is next opened joints.
Now Multi temp glue Not so good. It has the traits of a low temp melt glue to be able to work in a low temp gun. So basically you dont want to use Multi temp at all . Goes in the category of low temp. <place in trash can and put to curb>
What you want is High Temp glue and High temp gun. If you are dead set on using a hot glue gun. Again personally after having build four renditions of my ODST armor each one a step further along on quality and technique in the last 2 years. I have no use for Hot glue any longer in my basic construction.
Super Glue. Has good traits fast setting and is a solid bond. Trade off here is it tends to make the joint place almost solid. I would call it crystallize basically. I am sure some of the tech savvy can correct my terms for me. Super glue joints do not want to flex at all Which tends to mean it is not good to use in area that will have to flex. The end result for those joints is they tend to tear. Also on the trade off Super glue does have a bit of an odor problem and tends to instantly bond skin. Not so fun.
Contact cement. aka Weld wood from Dap Barge Cement (used in leather work and actually Barge is supposed to be stronger than Contact cement) Also may be found in other names but can be picked up at Lowes/Home Depot and home improvement stores in Quart cans. Pint cans and small 6 OZ bottles (which are great to carry in your costume first aid kit). Where super glue is generally a you have one shot to get your joint correct with an instant bond. Contact cement requires you to cover both sides of the joint with the glue. Wait up to 20 minutes for the glue to basically become dry to your touch before making the bond. If you lightly place the two pieces together you can for a short period pull the joint back apart to realign the piece if alignment is not correct. Once you have your alignment correct you push the two pieces together firmly to finish the joint. At this point if you try to separate the joint it will most likely tear just like a super glue joint. The other difference here at this point is a contact cement joint is much more flexible then a super glue generated joint. Now contact cement as well has a bit of an odor to it that bugs some people and is recommended to be used in a well ventilated area just like super glue. In the case of both types of glue nytrile gloves are a good thing to have if you have sensitive skin or are worried about skin contact.
Now any of your joints that are in high flex points. In the case of my armor my AB section where the side panels join the center plate for instance need to be reinforced from the back. In my case I simply use 3mm craft Foam as a reinforcement across the joint area. Also both super glue and contact cement joints can be sanded on the surface when dry to allow you to clean up joints. Hot glue will not take sanding and will simply clog up your sand paper and want to tear.
Now on the Flip. Contact cement does not work well/easily for attaching strapping to your armor. It does not like adhering for some reason. <again more technical than I care to get or be> What I have found so I dont have to have multiple glues on hand is I will adhere my strapping with contact cement and then place a 3mm craft foam cover over the joint area covering the end of the strap and about an inch around it to strengthen the connection..
Okay that is the short break down I think. <eyes the wall of the text> yeah short. Again I will state my wife Ashuraa and I are about as anti Hot glue as we can get so we will harp about not using it. Just simply because we have had enough bad experiences and a couple well placed lectures from a particular other Colonial spartan in our ranks that can spend hours explaining in technical detail why and how come.