Last night I had a go at Apologist-pattern True-scaling and built one Tactical and one Assault marines.
Considering I don't have much experience sculpting I think it came out alright, although I definitely lack the skill and patience to build a whole army of these guys! So I now have even more respect for those few who have!
Any pointers would be helpful. I used Pro-Create and Doghouse's trick of vaseline on the round end of the sculpting tool to smooth everything out and not leave fingerprints. What I found hard was creating any sort of detail--the sculpting tool would not cut cleanly, and I have some clay shapers but couldn't do much with those (perhaps I am using them wrong?). So the models are pretty rough around the edges.
I'd originally planned to use plasticard for the shoulder pad rims, but had difficulty getting it to stay down, so didn't.
This guy is a Tactical marine. I tried to add a raised round plate on his chest piece.


Here's an assault marine, using a MaxMini jump pack (which I think look a little large for regular-scale marines). The light doesn't let you make it out so well, but he's got an oval chest-plate, with a rectangular piece of armour coming down over the belt.


Like I said, any tips on how to improve sculpting very much appreciated! :)