Well despite having a seal from the Healey Surgeons, I just spent quite a while cursing that installation... Having read the previous posts I tried 'sliding' it in - from the end. I couldn't get it passed about 1 1/2" before it slipped out of the channel. In the end I pushed one side of the 'T' into the slot and then using a blunt screw driver pushed the other side in to the opposite side. The bulk of the seal went in reasonably quickly doing this, and I worked from the centre of the windscreen out to the sides. However I couldn't keep the last 5" or so in the channel as it went around the sharper curve at the edge of the windscreen. I used the screws that insert through the seal at the ends to hold it in place - but the 'T' part still resisted staying in the channel. I've placed the windscreen back on the car, though haven't bolted it down properly as yet - patience, and light, were wearing out, so I canned it for the day...
I can see the seal slightly sits out from the edge of the chrome as the previous seal did (that I didn't fit, but was on the car already) at the corners. The only improvement really is that the new one isn't split where it curves down into the door hinge area. Is this fit normal, or is there something I can do to improve it next time I fit a seal - sounds like they need replacing periodically?