What brand of fibreglass roof?
This is how my flexiglass one is mounted (the front is almost standard, the back is completely custom):
Windscreen frame latches:
Front panel rear/side latches:
Rear section latches (x4):
sorry about the poor quality of the last photo, I uploaded it ages ago for someone...
Anyway the system works good enough. It makes taking both panels on and off a very simple easy quick job
.
However the front panel I usually leave on when 4wding. And when the vehicle starts twisting and flexing it has a habit of popping the clips undone due to the amount of flex in a Sierra body.