Here are some pics of the current state of my Vader (with a Stormtrooper as comparison). So far all I did was lower the dome (dremeled the hell out of the top of the head) and padded the arms. The rest is just posing and futzing.
He currently stands at pretty much exactly 35 cm (13 3/4 inch). If Vader is supposed to be about 202 cm tall, he should be 33.66 cm in 1/6. So my goal is reduce him by a bit more than a cm. His shoulders also need to be more narrow, and I believe his forearms should be a bit shorter.
I am struggling a bit with where I should actually take the height away from, as I like his proportions aside from the shoulders and arms. I think best would be to reduce both the torso and legs by half a cm each. Any suggestions or other ideas?