Welcome to the "I'm sure they made this top too small!" club. Heat, stretch, and take a break. Put the car and the top in the sun. Just a note to myself, do not wait until it is raining in November to put the top up again. Borrow a commercial heat gun. Collapse the bows down. Do you have the front and real steel pieces. I bought a leather punch set at Harbor Freight, very handy. Then go to town! I marked the center front and back with caulk. I first installed the back bar. Then went to the front and installed the two side snaps. Of course with a lot of pulling and strtching and adding heat. Take the top off and punch a hole, put it back on, make the next hole, more stretching, pulling, and more heat. 3 hours later, DONE!
Best of luck!
Scott in CA
PS a Moss vinyl top shown