My uniformed duty experience with carry systems for a secondary: pants pocket (front or rear, loose or inside a wallet holster); jacket pocket (interior or exterior, loose or inside a wallet holster); shoulder rig under jacket or under shirt; under shirt attached to straps of body armor (and some of my fellow officers, including women, prefer a custom sewn holster to the front of the vest cover for faster access); ankle rig while wearing 'jump' style boots (I once worked with a partner who wore a commercially available boot with a holster). I also considered for a short time a concealment method on the duty belt, also a favored carry by my peers.
Our regs for uniformed carry of a auxilliary weapon are rather strict, the qual course is demanding from the standpoint of security, concealability and access from varied positions of disadvantage, and though the presentation times required in the course are somewhat liberal the level required for qualification is not (reduced size target and hit zone, higher percentage of CM hits). In the qual course we found the most secure carry to be: under shirt attached to vest; the fastest: attached to front of vest and ankle rigs.
My personal favorite for 15+ years: ankle rig. Compromises in that period: one of the three attachment mechanisms becoming undone, though the rig remained in place it was not as secure as it could have been; one occasion vaulting a fence where the weapon was separated from the holster and I had to recover it (heard it, saw it, got it).
For a second handgun in tactical operations, I first started 22+ years ago with a vertical shoulder rig; went to the master hand access cross draw, chest style military holster; went to strong side carry of both pistols (belt height and dropped combined, which many of our tactical operators still prefer); returned to the chest style; and now have a holster chest mounted for off hand (our term for 'weak hand') cross draw access.
The reason for this is that the sole use for this holster is for my primary pistol should I need to go hands free or transition to my secondary. The transition technique I use captures the primary in my off hand while my master hand goes to the secondary placed in a dropped strong side thigh rig (Safariland 6004). The custom positioning of the cross draw chest holster permits me to holster with the off hand without interfering with the mount of a shoulder weapon.
Operationally, we'd have two handguns with us only if the handgun was to be the operator's primary weapon. In a situation where the operator were employing a shoulder weapon, they'd likely take just one handgun though I've seen members carry two. In training most will always have both handguns in addition to their shoulder weapons, usually as a matter of training time expedience.
Other methods in use by members of my unit: shoulder rigs, strong hand chest mount cross draws, strong hand cross draw belt level (but drawn with the off hand), and off hand belt level (a holster on each hip). I have yet to see a shooter in my unit try a off hand cross draw belt level; then again it boils down to balancing security and accessibility in the operational environment, and what works for the individual operator.
Thanks for staying, if you have, with another of my long winded posts, this time highlighted by the many (..)s.
Miratio, Incursio, et Sestinato...
[This message has been edited by SKN (edited 12-19-98).]