sysmoUSIM variants and alternatives

(Posting to the OpenBSC list because I figured that the set of people who issue their own SIMs probably has a good overlap with the set of people who operate their own physical GSM networks.) I am shopping for some non-carrier-branded, non-carrier-issued SIM cards for use in testing my FreeCalypso GSM MS devices (specifically, testing of the SIM interface in isolation without bringing up radio, as well as radio and full MS functionality testing with a base station simulator like CMU200 instead of live networks), and the only product I found so far is sysmoUSIM - if anyone else makes a similar product ("generic" SIM cards for tinkerers), I would like to know about it. In the case of sysmo(U)SIM cards, it looks like 2FF-only cards are no longer available, and the current choices are 2FF+3FF or 2FF+4FF. My question is: if I only want 2FF and have no interest in 3FF or 4FF, which variant should I buy? In other words, which variant is mechanically stronger and less likely to break in 2FF-only usage in various kinds in 2FF sockets? TIA, Mychaela