aye - I know what you mean. just follow any of the clone lid makers in the WIPs and they all complain about the same thing - eg SGB's on going sculpt of the AT RT on CE
only 2 lids that i know of are pghfett's and pghfett's badly recasted lid from SFP. neither of which I have in my possession; but on pics look like their backsides are shorter.
but, if u having said that - the biker lid above of mine is a Rubies lid, and although abit tight on my 59cm head, it does fit.
we will see how the MB lid goes ;P
oh was abt to say - lots of clone troopers are used to cutting up their lids to fit their heads. its a small sacrifice we all make in order to get screen accurate lids. I say go for accuracy, a clone trooper WILL find a way to get the lid onto our heads.
Nate