I purchased a BPL Absaroka, and want to modify it to accommodate a Platy hydration system.

Here's the pack:
http://www.backpackinglight.com/cgi-bin/backpackinglight/bpl_absaroka_backpack.html


I plan to upgrade my pack liner to a ZPacks full bag cuben roll top dry bag. I would place the Platy bag in between the backpack and liner.

There is no opening for the hydration tube, and the top of the bag is a roll top closure.
Here is a picture of the inside of the bag with the Platy inside:


I was thinking I could sew in a loop with a snap to hold up the Platy bag. I could attach this loop to the folded over seam.

However, I'm concerned that the weight of the water filled Platy will pull down on the pack as shown here:


My other thought is that a Platy sandwiched between a backpack and a full dry bag will not apply the weight load directly to the backpack, but instead be trapped in position through friction/pressure.

Do you think I need a loop to hold up the bladder? If I need one, do you think it's OK to install it where I indicated?

My last question pertains to routing the drinking tube through the pack itself. I know the pack is designed to be water resistant, but since all my gear will be in a dry sack, I'm not concerned about this. I was thinking I could sew on a patch with a slit in it that could act like a beak on a rain fly in order to direct any overhead water away from the opening.

This is where I'm thinking I could route the tube:


Is this a good spot, or would you put the hole somewhere else?

What do you think about this idea? What material would you use? Would you seal the seams?

Do you have any other suggestions?

I wouldn't put a snap to hold the bottle upright, I would just let it sit on the bottom of the pack sandwiched between your dry bag and back panel. I would install a plastic snap grommet large enough to put the tube through, may have to take the bite valve off to do this. This would be a way to do it without any sewing.