After posting my first attempt at a corrected height and getting some feedback on it, I reworked him to increase his height even more and finally reaching an acceptable size. The main difference was using the middle torso from Thaal Sinestro (Green Lantern vs Thaal Sinestro 2pk). It required a lot of sanding and modification to get it to fit, but I was finally able to make it work.

I decided to shave some of his hair off to give him his modern look. This time around I removed the collar and painted one on. The wave 3 Sin's neck isn't as long as Thaal's and I felt the collar piece made his neck look even shorter. I also repainted him to achieve a lighter yellow color on his uniform.

Special thanks to Lesternessman for his tips!