http://www.dakkadakka.com/dakkaforum/posts/list/8.page JForum - http://www.jforum.net IG regiment. Some interesting parts I found are for legionaries from Kromlech:

https://bitsofwar.com/home/451-stygian-torsos.html
https://bitsofwar.com/home/146-stygian-legs-.html
Even if they are intended for "counts as space marines" they don't seem too bulky and leaving out the enormous shoulder plates this might possibly work, if they are not far too tall.

Can anybody tell me, if these legionaries are the size of the "old" marines or more like the new primaris marines?]]> http://www.dakkadakka.com/dakkaforum/posts/preList/777704/10499125.page http://www.dakkadakka.com/dakkaforum/posts/preList/777704/10499125.page GMT
I think kromlech label things 'prime' if they are primaris size (eg: https://bitsofwar.com/home/827-prime-legionaries-bodies-tabards.html)]]> http://www.dakkadakka.com/dakkaforum/posts/preList/777704/10499494.page http://www.dakkadakka.com/dakkaforum/posts/preList/777704/10499494.page GMT http://www.dakkadakka.com/dakkaforum/posts/preList/777704/10499518.page http://www.dakkadakka.com/dakkaforum/posts/preList/777704/10499518.page GMT