Anyone got experience of fitting one of these ?

I've fitted all new rubber to almost all of the car this weekend but I can't get the 3/4 window seals to fit.
After 5 hours I managed to fudge one on but scratched the car in the process - I almost cried.

I can get the seal around the upper and lower curved edges of the window but when that's on, the front edge (the one inside the door gap) just will not go into the slot, it's hanging loose. It's as though the seal is built for a larger window.

Now the seal is on but the front edge gets pulled out whenever I shut the door and the window needs one hell of a shove to shut it.
The dealer assured me that the seal I've got is the right one. It looks the same as the one that came off the car.

If you can remember how to fit one I'd love to know the trick !