OK, so what I did last with my car's gear knob and gaiter didn't work well. It looked great, but there was one problem; shift into Reverse, then the gaiter will run out of material and get pulled out by the shift knob. Even if the gaiter didn't get pulled out, it'll get stretched a bit at the side where 1st gear is, so eventually the wear will eat a hole into the gaiter, just like what happened to the original gaiter (this one is actually a second one I had someone make for me).
Obviously, this is caused by the new knob being significantly shorter than the old one:
Anyway, to make a long story short, I sawed the old one off..
...and after some sanding to rid those unsightly saw ripples, I used some double-sided tape, and fixed the sawed-off bottom to the shift stick and gaiter. So there, the neck of the gaiter is contantly positioned about an inch lower than before, about the same as it'd always been with the old shift knob.
Slapped the new knob back on. The shifter is in Reverse and there is noticably a lot more slack towards the direction of 1st gear, just like how it used to be. The whole thing looks a bit weird though. I tried covering the aluminium ring in some textured black sticker, but the end result wasn't very pretty, so I got rid of it. I think I should just get another shift knob and be done with it.
Phew, so much trouble just for a stupid shift knob. I know I should ignore it. It's insignificant. A lot of other cars have a gap that leaves the shift stick visible. I know that. A lot of other cars have shift knobs that do not match too. I know that too. But I effin couldn't ignore it. I think I'm OCD :(