1. Following sheet specs is always a funny thing. Sometimes they're there for good reason and sometimes, not so much. If it makes sense to make the sign out of HDU, and you know how to make a good HDU sign, everyone will likely be better off with you just making it out of HDU and moving on.
2. PVC is not a material you blast. You CNC route it. You simply cannot blast it. It won't work.
3. Komatex IS NOT exterior grade PVC. Komacel is Kommerling's exterior grade PVC. A cheap trick to finding if a PVC sheet good is exterior grade is if it's glossy. Now this doesn't work all the time, but it works most of the time.
4. There is absolutely nothing wrong with using exterior PVC, in exterior sign applications. Like any material, it has it's pros and cons. HDU is hardly a perfect material. It's expensive, it's easy to damage, you can't screw into it, it's dusty, and has no grain structure which can result in warping. With that said, it's still a great material, just like PVC can be.
5. You do not need to treat the edge of exterior grade PVC. It's a cellular PVC. The water cannot soak into it. It won't rot.
6. Generally speaking, I'd stay away from 1/2" PVC for exterior signs. Great for interior, but exterior it's on the thin side. It will work in certain applications though. Smaller signs it's fine. Medium wall mount signs it should also be fine if you mount it properly. For medium sized signs, 3/4" PVC is what you want to buy. For medium to large signs, just buy the 1" PVC. It's cheaper than 20lb Duna and slightly more expensive than 15lb Duna at the same thickness. It's a competitively priced material all things considered. On large signs, you do have to make it correctly (just like HDU). Generally speaking once the signs start getting to be around 4x8, you're better off going with HDU. The weight on a big PVC sign is brutal compared to HDU.
