Keep this in mind (though I'm not sure what you do about it): My seal has shrunk over the (20) years, retreating about 1/8" on each end.
Perhaps make it as long as you can and still look right or at the very least let it relax for a few days after installing it since the install often involves stretching the seal to get it to slip thru the groove.
Like a haircut... You can alsways trim off more later, hard to put any back.
Come to think of it, my hair has receded quite a bit in those same 20 years.