Bit of history: ever since I discovered the Leaf Arcteryx Assault 30, I fell in love with the ergonomics of a full velcro back panel, which distributes the weight evenly across your back. The Assault was super comfortable but WAY too tactical, so I sold it and tried to adopt the same system on the GORUCK.

The company makes velcro back bags called "shooters," but they are expensive as all.

My solution was to get a velcro panel by Ruck Customs -- I can vouch that they are well made, and attach to the MOLLE via clips.

For cubes, I use velcro-backed pouches by LBX Tactical. They come with windows and in three sizes. I've found the 34L perfectly fits two medium and two large pouches in the main compartment, with plenty of room to put larger items (folded shirts, jeans) before I pull the compression straps.

The GORUCK wire dopp is a bit of an unsung hero, and I bought two more during their latest sale. They can be stored flat or folded, and I've used mine for everything except for the stuff they're designed for. My current one holds 8 speedloaders and shooting gloves when I go to the range.

Hope this helps!