Other than the Corvette specialists (google search) any professional car hood/soft top fitting firm should be able to help you. The top is designed to be tight and it's important when erecting it to secure the rear studs first then the three front clips. When lowering undo the front clips first then release the rear studs. Engaging the rear studs should just compress the rear weather seal against the body. To get this correct you can adjust the engagement length of the studs. The front clips can be adjusted too to optimise the clamp force. The frame mounting can be moved to optimise the soft top alignment. The frame is secured to the body 'B' posts with two screws each side. These are arrowed red in the picture below...

The frame can be moved up and down and forward and back by slackening off these screws. Be aware that the threads of these bolts or of the plate they go into are often stripped from previous ham-fisted adjustment. It might be worth trying these adjustments yourself to see if you can effect any improvement before giving it to a professional.
This thread might help too.
I fitted a new top to my '71 which did need quite a lot of adjustment to the frame before fitting the cover.
