Convertible top adjustment
From E30 Zone Wiki
Firstly you need to loosten off all the securing nuts/bolts, then adjust the height using the pic below.. once done leave the bottom 4 nuts loose so the roof can still move foward/back.
then close the top onto the windscreen (leave the lid open) and latch it with both latches. Now you can shim the top mounting into the correct place. Once you have done this, you can then secure all the nuts/bolts.
