I have a SOE holster and would suggest that it doesn't meet a definitive answer to holstering an M2.
Firstly lets look at the quality of construction; excellent, cant be faulted!The design, is IMHO, a problem. It does not allow for the use of filters or for non-standard tailcaps. Further, it also, unless adjusted very tightly, doesn't secure the bezel well enough. Experience indicates that in strenuous activity the strap securing the M2's bezel will slip and allow the M2 to be lost! I think this design fault could have been avoided by the use of some form of simple plastic bezel mould which would have prevented any possibility of the bezel strap slipping!
IMO the best holster for the M2 is Surefire's own. Although there is one of the plastic type that holds the M2 bezel up only, there is another one which will hold it either bezel up or down. I know because I have both of them here as I write this but I cant find the part no at the moment....perhaps Al Windler can help? At any rate although neither of these holster is IMHO ideal they are probably the best out there at the present time!
Doug