I still live with the trauma of putting mine in. On the first attempt, I
destroyed the seal and had to order another one for the next try.
You are probably aware of the cord that you place in there. In addition
to that I made sure it was a warm enough day with lots of sunshine
warming the seal. I used masking tape on some of the transition areas on
the frame where the cord wanted to catch to eliminate and rough areas.
Also I used vegetable oil as a lubricant, just coated the seal with it
using a paper towel.