If you make something like that, Don't get one of those ugly $70 crusader helms with the straight sides and flat top.
Get one with a top that's sloped in some way. It looks better and will allow the torse to stay on.
Something like this would be good, as it will hold the torse and will allow you to lift the visor for a breather when it gets too stuffy.
'Luck is the residue of design.' - John Milton
'Let the world tremble as it senses all you are about to accomplish.' - Luís de Camões