How to deal with HT bad seals between front/ quarter windows?

The metal piece between the door glass and the 1/4 glass is stainless not chrome. The stainless piece is held to the edge of the glass with "glass setting tape".(and on my convertible, it's also riveted to the pot metal glass retainer) The rubber seal is a separate piece and can easily be replaced. It just slides out the bottom of the stainless piece. The new seal will slide in...no glue needed.

I got a pair of these from DTM for my '65 Barracuda - just wondering of any "tricks" to get them slid into the stainless trim piece. they go VERY tight....any good experience is apprecaited as I have never done this before and afraid I will tear the new ones up....thanks in advance to anyone who can share some knowledge at me....