I have a couple of these and they both measure around the 40.2 mark. Every one I have ever seen has been a studio release poster so no NSS info. So it looks to me like you are in good shape. Hope this helps.
Since it's a late 80's WB release, I wouldn't be surprised if a good chunk of the rolled examples (along with some of the folded) were actually video one sheets, basically indistinguishable from the theatrical version.
I don't have any direct info that this is the case, since I don't collect on this specific title, but it's always a possibility with WB posters from this era (80's to very early 90's).
This is not to say that your posters are not originals, I just wanted give you a heads up to the possibility.