I can not disagree with you Brad, I have no experience with the home brew product. I do not think I would use it on a customer car either. But then I would never be in the position to do a "customer car". I have two 56 Ford F-100 short box trucks in progress and a 56 F-250 long bed that I put duallies under with smoke stacks, big truck mirrors, cab lights, and a flatbed on. The 250 is kind of a test project for trying new products. Problem is the more I work on it, the more I love it and dont want to have issues with it down the road either. The cab floor (underside) and part of the engine side firewall is done with SPI Bedliner. I still have part of a gallon left. Im probably going to try the home brew on the inside of the back cab wall and maybe underneath the cab roof....not sure yet. I see in an earlier post it was mentioned that Lizzard Skin H/N might be latex and ceramic microspheres. Not to be confused with the two part lizzard skin bedliner. I have to do more research on that, but if in fact lizzard skin makes a ceramic microspheres in latex paint product, I might just follow up on the home brew to replicate that for interior use only.
Funny you brought up the home made dynamat. I have heard mixed reviews on using the big box store peel and stick insulation instead of the high end products. Some horror stories caution against it becasue its a tar base. In warm weather, the aspahult base gives off the tar smell. In many cases, it gets hot enough to let loose, especially from the roof after sitting in the sun. Dark colors seem to be more prone to the problem. In other cases, guys have had luck with it and never had anything negative to say about it. One of them "toss the dice" options we all have when restoring our cars and trucks. Anytime we try and cut corners by saving on high end products, we take the risk of paying double to fix it with a lot of hard work thrown in for a screw up.
I did a follow up post on that like I posted to see if anyone had anything to add after the product had been applied for awhile (home brew lizzard skin).