I have used a DC helmet for a number of years in a variety of (aerobatic) aircraft. The advantage over the other types that I tried at the time is that it is smaller and lighter; I guess that that is also its disadvantage in a crash situation. The chin strap is not the best, but there has been no evidence of ithe helmet moving around even during extreme aeros - so perhaps it really would stay on in an impact. I seem to recall you can get a visor for it, but have never seen one. Certainly it is feasible wearing specs with the helmet.