After wearing this kit for several years I can not imagine any way it can comfortably be worn on the belt with any weight in it. I suppose you could use extension straps instead of the L straps on the top strap fittings but it wouldn't be very secure and would be a pain when you lay down since its so large for a belt piece.
I have not seen any buckles of any kind other than the L straps. The brass U located on the corner of the L hooks on the top of the Bren pouch if you can't tell from photos. Many bags do not have brass fittings on the bottom as they have been taken off at some point. For this reason it can be difficult to attach it to the back securely. I attach mine to the side fittings at the top instead. This is very snug and hard to get on/off but it works.
I hope I have been helpful.
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