Nearing completion of my first myog pack, made out of xpac, and I want to make it waterproof enough to keep my sleeping bag dry through heavy rain without a liner. Should I use diluted silicon, seam grip, or something else?

.. seam grip on my last VX07 pack. Worked well. Straight out of the tube.

Good luck!

Oh, and do work in a well ventilated room. =)

Thanks, Dan. Did you use it on the inside, outside, or both? If on the outside, how noticeable is it when dry?

Don't have the pack next to me right now. But I remember doing all inside seams first then the outside at the most stressed and exposed seams. I did it just as much for strength as for waterproofing.
The surface gets a slightly shiny, transparent appearance, but it's not a ugly or anything so I don't mind that. Once dry nothing has stuck to it so that's also a no worry.

Good luck!

Thanks again, Dan