Originally Posted by HaChayalBoded
They were never designed for it, although it can work it doesn't quite sit "nicely".
I have two US-30's and mounting them together is awkward. Unless I use one set of extra long straps through the D rings of the bottom one and the tops ones and then clicked into just the top bag.
Mike, if I can suggest something. Add a set of rectangular D rings like you have all over the bag to the loops that hold the female buckles on the top of the bags. This alone will allow you to mount two identically sized bags to one another.
I found these and will probably get them.
Mounting two of the same bag is not problem at all. Simply attach the 'base bag' to the bike, using the included Alloy Hook Straps. Then stack the second bag and thread the Alloy Hooks on the upper bag into the web loops on the base of the base bag and cinch down. Simple and rock solid. Although obviously 2 x 30-liter packs stacked creates something of a skyscraper. 2 x US-20 is more advisable.
The above relates to the current edition of our US Packs, which utilize Alloy Hook Straps. Let me know if you have the previous versions (which all have rectangular plastic rings on the top for precisely that purpose), so I can explain how to do it with them.
Hope that helps!