I just received my Standard Carrier frame for my ML3 and fitted my Mountainsmith Day lumbar pack (which I had for many years) using the waist strap around the outside of the frame.
I looks great and even matches the color of my cobalt frame. The bag will hold up to 14 liters. There is no interference with the brake levers and the bike folds perfectly with the bag attached.



In the future I may drill the rivets out on the side rails to remove or trim the size down a bit.

.

If combined with my Relevate Seat Bag (8-16 liters) it will provide a good bit of storage.



So far I'm very happy with the results.
Oh yeah, just tested, I can easily fit a 6 pack of beer in the front bag!