Sorry for the delayed response. I was running the Missouri Rally this weekend. What a great time!
For the tube, I just drilled the top to a size that would let the tube pass through. I used a 90 degree elbow as I didn't want it to stick straight up for my application. I didn't seal it. You need venting anyway, or you can't drink very fast, and can get light headed trying to quench your thirst.
I just used a step bit, and stopped when it passed through. To keep it in the jug, I used zip ties. They also double as hose clamps.
I'll try to get some pics when I clean it out over the next day or two.
I ran this set-up on the HD for IBR21 and just adapted it to the GSA.