Hi guys, just thought i'd run past my harness system idea.
See attached pic - I will have the usual straps coming off the shoulders and passing through the back plate to 'D' clips at the top of the JP (these are not shown on my pic though.
I have gotten hold of an old backpack and removed all except the straps and the back material. I have then added a plate to the back to reinforce it. I have next attached, using brackets, some metal rod bent as shown in the pic. These rods will then slide into tubes on the JP itself (in affect the JP will slot onto the rods.
The JP will then have the shoulder straps to stop it 'falling' backwards.
Will post pics once it is finished
PS sorry for the cruddy pic (whipped up in about two minutes :o)