Guys, thanks for the input. This is helpful.
BoobooFett I especially appreciate your take: it's so true that "heavy" is relative. As I mentioned before- after wearing my resin Java ep. II clone helmet on troops (my neck would actually be sore afterward) the MR Fett may feel like a feather.
And I don't have a smallish head so hopefully any wobbling can be fixed by extra padding as you mentioned.
Plus I have to believe that the thrill of being Boba Fett outweighs (pardon the pun) any slight discomfort from a solid helmet. 
Tell me please do you wear a "riot chin strap" or whatever it's called for your MR? I would imagine it cuts down on any wobble as well. Or is the riot strap thing kind of a rarity? Thanks.