Here are some pics of how I attached my freecycle topbox to my renthal rack.
Grumpy dad was not impressed my me ‘borrowing’ his stainless steel bolts, but I am very chuffed with myself considering I didn’t even do metalwork at school ( I had to do cookery and sewing: women, know your limits!!!). The bolts have rubber washers either side, so no rattling around, and I filled the two old holes with sealant. I found some aluminium angle and butchered this to length.
Well, I’ve done 1000 miles so far and it hasn’t fallen off although I learnt in the nick of time that locking nuts are best!