Hey there, it's NOT the ROTJ Squiddo yet, it's a random Quarren as of now, with a little luck I should get around to make the Tessek Quarren next week.
I certainly do recommend the smoothest Fine material, it's pricy but worth it imo. The white processed stuff is OKish but lacks detail and has a slightly rough surface.
I have no 1/6 scale figures myself, so no that's not possible to take pics next to something "known". Neither have I printed any of the heads myself. The size of them is based on the measurements I got here and from the pics Steven send ( and posted in this thread here too ) so the size should be pretty spot on. Each model specifies the size on the page, if you are not sure about the size, you can compare those measurements to heads you own.
As for squashed stuff, that never happened to me at shapeways so far and their prints have been great quality, should there be issues with prints, they react fast and make sure you end up with a product you are satisfied with.
EDIT: Btw I also made these last week:
I could export them in 1:6 if they are useful to you guys. Is there any interest in those or weaponry and alike?