[welshcameraman]

I am not sure about the percentage of front to back, but make sure you balance left and right sides equally. I also used to put tons of kit on top of the back rack as well.

I also used a Jack Wolfskin bar bag for my camera kit...an old olympus om system at the time.The reason for that was the interior sizes matched perfectly the camera bag I used to use, so it was just a matter of transferring the dividers back and fore.

Like you I used to use a vango... a micro 3, which was terrific. You could leave the inner attatched and it went up in seconds, but did need to have at least 4 good fixings. Eventually changed it for a Terra Nova voyager,which is 10- 11 years old now and I am still using it.