I have carried the Jumbo (previously called the Jumbo Fat Boy) for somewhat more than two years and can attest that it is a very, very good tool. Everything that Maxpedition makes tends to be overbuilt for the purpose which makes for a bag that is both well built and which will withstand hard use.
The gun pocket is huge. It will accommodate a full size 1911 and my XD45 Service fits quite nicely with room for an extra large ammo mag. I just can't give the velcro "holster" that they sell as an extra my whole hearted endorsement. It works, but just barely. There are other velcro backed holsters available that to the job better.
Overall the Jumbo is an outstanding carry bag and I recommend it highly.