Hello
Poser - User, welcome to Posetteforever.
I really do like the work I have seen on your website. I have bookmarked it so to go back again.
I had a problem like that for one of my pictures too. It was a ring that I needed.
For your collar, I am not sure how detailed you want it to be.
If all you need is something to close the gap from the suit to the helmet. I offer this idea. Use the torus primitive prop from
Poser turn it to match the gap you want to close, change its size and move it to where you want it. Depending on the style, maybe the helmet, or the neck of the person you can make to be the parent for the torus. then give is a texture that give it the look of the suit.
Once again, welcome to Posetteforever.