The weather stripping around the top of my windows isn't correct is it? Both doors seem about an inch short. Does it shrink? It's the original rubber.

Yes, those seals do tend to shrink, and the "replacement" parts I have seen are most often cut too short to begin with.

Rubber will shrink, but the real problem was the material was pulled through the channel then cut. You should cut the rubber to length, and install. When you pull through the rubber stretches. You can lubricate the track but it has memory and it there is ANY tension on it, it will appear to "shrink" as it returns to the original size.
This is also a problem for the targa to window seals on the roof.

The problem I have seen with replacements of this part is the material was cut too short by the parts supplier to begin with, not stretched and cut short by installer.

Well I can tell you we ship them out for you to cut. Not sure why anyone would do it any other way.

When I get to that point I'll be in touch

I also have the "correct" profile. Porsche superseded the "correct" part somewhere in 74, and went cheap by using the 911 scraper. It was a cost cutting measure, but they tend to grab, more so when new. So pre 74 this is the correct profile installed.
(shown installed on my 75)
I do have both.

There's a way to install the squeegees without pulling them through the track. you lay it over the channel and use a wood dowel or other small blunt item to "snap" it into place.

I will totally agree with this statement. Even the lubed install will need to return to size. Use lots of lube... soapy water. pick a rainy weekend, install it..... wait to cut it for a few days or weeks.

I also tried to "return" it to size by pushing it back.

The front trunk bulkhead seal I got from you at 914Rubber was sent that way...a little long and cut to fit. A well made part done right. I'll get my next set of seals from you.

I got my window scraper seals from Mikey914. Plenty of extra length so you can cut to fit. Highly recommend! Also got my door end cap seals from him. Dont forget about those.

Hey, my 46 year old end caps are perfectly cromulent! Damn, those things are petrified hard, and sharp too...you do not want to bang your head on my door end caps.
Click to view attachment

The door end cap seals are at the outer end of the door. Basically the plastic end extension of the scraper seals, below the side targa seal.

Get a $6 set of plastic body tools from HF. They're great for pushing in seals