Which HMG pack?

I don't trust any pack to be completely waterproof when packrafting. I concur with the use of dry bags – there are plenty of UL CF drybags out there.

My current Porter is taped (Black – 150D) and because it is sealed so well, I have never gotten moisture inside the pack. Not sure how one does that given it is taped. This would be like getting water inside your tent that has taped seams and not drying it out, thereby causing the tape to rot and peel. If you DO get water inside your pack, dry it out after your trip. Remove the stays and fold the pack inside out.

I think most of the water that came in on my HMG packs when hiking in driving rain was through the seam where the haul loop and the top of the shoulder straps enter the pack body. Mine had no tape inside along this seam. I got water puddling in my pack after prolonged rain exposure. Aquaseal works brilliantly on the outside face fabric on HMG cuben. I stuff the pack really full until the seams are taut, and then run a thin bead of Aquaseal along the outside of the pack seams. You can do the spots where the webbing straps and other harness bits penetrate the pack seams as well, carefully saturating the webbing or material so it does not conduct water into the surrounding seam. It's not the world's prettiest thing unless you are careful, but then the packs are pretty damn ugly to start with.