I did this fix very recently and found that there is a small tab or blade of metal on the body at the two channel tops that became my starting point for installation. I pushed the 914 Rubber piece onto that tab, (and there may be a screw involved on some cars) and then proceeded to manhandle the corners into their correct fit.
The middle top of the seal was dangling as were the two channel pieces at that point but the two corners were tight and felt and looked rightish.
I used a mixture of fruity soap, hand lotion, green liquid dish soap (color matters) and beer to lube the vertical channels and me and then pushed the interior side into the channel inch by inch with a well rounded 9" long plastic tool (used in the Tiffany method of stained glass/ copper foil artwork).
Then with the careful application of more and more beer, and a careful dousing of the lube recipe noted herein, i pushed the exterior side of the channel-rubber into the aluminum channel. From the factory the aluminum channel is crimped to trap the factory seal so gently pry open that part of the channel or you will not get the vertical all in.
Lastly, dont have any more beer and get out your new sharp 4" long blade and clamp it in vice grips, dip it in your lube solution and gently saw off the extra seal at the bottom AND NOTE HOW THE DOOR CLOSES TO FIND THE PERFECT ANGLE FOR THE BOTTOM CUT.
Sidebar: If you screw it up
, 914 Rubber has more for sale............