Well David, since you want to go down that road I'll play. Just how many times have you been in a life and death situation where you couldn't get to to your primary weapon. Just how many times have you been in a life or death situation? Just how many people to you know personally not heard of have been in a life or death situation? IMHO I think a number of people see's or hears about something and say I've got to have that, when in truth you really don't. It took me couple of years after I left the Sheriff's Office to realize I don't need a hi-cap weapon, I mean what are the odds of me getting in a fire-fight with a bunch of hostile's. That is really when I embraced the my favorite weapon the 1911. Just saying the odds of you ever needing do not justify having to carry the extra weight or responsibility of keeping track of another weapon.
If you're carrying a full size 1911 with a spare mag, you're already carrying more gun than 90% of the CCW'ers out there.
To the OP, if you're gonna get a G-16 ankle rig, get the Galco Ankle Glove. It's secure, comfortable and fast (for an ankle rig). Most ankle holsters can't do all three.