Actually, the V3 was based off of the actual screen used armor.
http://www.thedentedhelmet.com/f25/fp-armor-version-3-a-22811/
From what i understand the v4 is just some more tweaks to make it closer to the info they got back then for the V3. I believ the size is the same, as they got measurements from the actual armor at C4..cant see how that would change
But back onto the point of this thread...FP is still super busy, and had a personal matter as well (and moving as previously mentioned) It may be a little bit before he's back on track. He usually takes a little bit to respond to e-mails, but does get back to you. Im interested in a GMH helmet,but im waiting till he is caught up for the most part and back on a normal schedule.