Jayco Discovery boot leaks

I noticed that after some heavy rain that the boot on our fibreglass body 2010 Discovery contained a considerable quantity of water. Inspection of the boot lid revealed that the hinge had partially parted from the boot lid allowing rain to pass through the resultant gap. The hinge is secured to the lid with split rivets, many of which had failed resulting in the troublesome gap. I drilled out all the rivets intending to replace them all, but have realised that the underlying cause of the problem is that the boot attachment face for the hinge and the attachment face on the caravan body are not parallel when the boot is in the closed position. The stainless steel hinge is very rigid in the closed position and something had to give...and that's why it tore out the rivets.
Replacing the rivets wont solve the problem, its always been there and wont go away with the original design.
My real concern is that if I don't do it properly and carefully, I could crack the fiberglass lid or the caravan body

Has anyone else had this problem and have they found a way to get around it?