60mm is the max you can go, you need to remove the arm at the bottom that assists with folding the seat forward - you will see which one when you fold the seat forward
if you try to go further back several problems
1) rear bottom of the seat fouls the floor, and it wont sit down, will always "flop around"
2) you cannot move the rear bracket on the floor any further back, as you cannot get under there to tighten bolts
3) you will loose the rear bolt of the two at the front of the seat - IMHO very very bad juju
4) the side of the seat fouls the wheel arch
after lots and lots of R&D, we came up with a happy compromise of 60mm
enough for me to sit in the back, with the front seats ALL the way back, and still have room between front seat and my knee's
both Mike and I did it Clunky, but if you ask him nicely, he would do it
biggest problem we found was the cracking of the floor around where the bracket on the floor is bolted
if its cracked, get it welded up properly
under one side on mine was the Aux fuel tank - hence the "get it welded up properly"
we had a look at a few GQ's, and they were all the same

