Shrinking Weatherstrip

The strip that wipes the outside of the winding windows was sourced new for the Vogue when I re-fitted the winding windows. Referred to as door glass weatherstrip and a few other names,
I purchased mine in Australia and it appears similar to what is available at a few places here.
Unlike the original it has no reinforcing metal strip.

Trouble is - it shrinks!

Note also the waving lines where the clips are holding it inside the door.

The Vogue has "seen" two summers in active use now and the driver door weatherstrip is now about 22mm shorter than when I installed it.
The passenger side is a little better, but not much. The driver side is exposed to the Sun more than the passenger side and it shrunk first over the summer of 2013/2014 by about 15mm. (January/February is the peek of summer here.)

I have finally found something like the original with the metal strip buried in it and have ordered some from the UK.
I get the feeling that most Classic car restorations sit in garages most of the time and are not exposed to the weather much.