Have you wondered why those few "little" changes you asked for in your Speedster, Spyder or Coupe (or house, for that matter) suddenly add a LOT of time to the overall build?
Well, It's like this:
I've had an air leak from my convertible top since I installed it. The leak is from a pocket formed right behind the doors as the top material curves down to the car's body - It forms a scoop right there, funneling lots of air onto the driver's/passenger's outside shoulder. I fixed it on the driver's side years ago by lengthening the side window about 1" beyond the end of the door so that it extends to the rear of the pocket and seals the leak. Worked great, as the alternative would have been to move the entire top forward an inch and THAT ain't gonna happen. Remember - I built a CMC and nothing ever fit the first time.
Remember too, my windows are very different from what most of you have - Mine don't have a fabric border around them to give me a much larger glass area. I use a finned rubber channel around most of the glass and a bulbous rubber channel on the front just inside of the windshield left/right sides. Everything seals up nicely and I get minimal water intrusion. Air's another matter.
Anyway, I just got around to lengthening the passenger window last week, so I removed the old window and used it as a template to cut out a new piece of Lexan just a bit longer. That went reasonably easy, cutting it slowly with a Saber Saw and a 30 TPI saw blade.
BTW: I bought real Polycarbonate (Lexan) for this. If you use the stuff at Home Depot/Lowes it will probably be clear acrylic which is thinner (.097" as opposed to .125" or 1/8" that I used) flimsier, softer and tougher to cut - As the blade goes through, it melts the acrylic which then re-bonds right behind the blade. Lexan doesn't do that.
What really threw me a curve was getting the angle of the side glass right, to fit just behind the edges of the windshield. THAT took, like, three days of bending the mounts this way and that until it all matched up and sealed right. THEN heating the front lower corner of the Lexan to bend it in slightly to match the corner posts and allow the gasket to sneak behind the post when the door is closed - Add another day for that with tons of trying, bending, trying, bending, trying, all with a heat gun.
All that done, I moved on to the rubber seals all around and used the old ones as templates to save time, BUT screwed around with them to make them look nicer this time (Prettiness counts for something, doesn't it?). That was all day, today.
And THAT, boys and girls, is what happens when you ask for something "Special" on your builds. This was just a friggin side window. Imagine what happens when you ask for Cup Holders, or a 2-gauge dash or lowered seats. Nothing has zero affect.
You have to really appreciate what the crews at the builders are going through each and every day by adding all of those little custom touches to your cars. I'm not saying don't customize your cars...... Just realize that all that stuff takes time.