1970 300 need help with tight convertible top please

I have a 3 year old top on this car. It has been driven maybe 150 miles since the top was put on. It was super tight when we got it from the installer and kept it up for a while. Last time I did battle with it was about 2 years ago. Now I am starting again. I know it is way too tight and I am hoping I can make some adjustments??
Anyone know much about these tops?
Thanks
Howard
Author: challenger