im shopping for a helmet. im 5'8", 185, typical size head for proportions, I guess. I just tried on a shoei, size large, and it moved around a tiny bit. tried a medium, it was painful. im guessing I have to go with the large. next question is dot or snell? last question, is 3/4 reasonable safety, or do you suggest full face? I want to be safe, but not feel terribly incumbered. thoughts? If its DOT, is it ok, even thought its pretty cheap on amazon?