For all intents and purposes, the Swift Clamp looks like the most secure solution to my problem. But at $149.95, the clamp would more than twice as expensive as either of the straps it would be used on. Converting both straps using the Swift Clamp would require a $300.00 investment. To me, that seemed a bit excessive. Therefore, I looked for an alternative solution.
With a little more research, I stumbled across this YouTube video (by Lee, Enthusiast Photographer) that described using a standard Arca-Swiss style clamp affixed to the BlackRapid FastenR-3 D-ring that comes standard with all BlackRapid straps. The video also noted that you can use an OP/TECH USA Uni-Loop to connect the BlackRapid ConnectR-2 to your L-bracket for added security (shown below). If you aren't using an L-bracket but you are using a battery grip, you can also connect the Uni-Loop to the battery grip's hand strap mount.
* Note: This clamp is drilled for a 3/8"-16 screw and comes with a 1/4"-20 adapter bushing. The adapter bushing is required to fit the clamp to the BlackRapid D-ring. While I haven't noticed any problems using the adapter bushing, I'd suggest getting a clamp threaded for a 1/4"-20 screw instead (like the Kirk QRC-1, Sunwayfoto DDC-26 or possibly a larger clamp with a 1/4"-20 thread size).
For even greater security, you can use Loctite between the BlackRapid D-ring and your clamp to ensure they don't work themselves loose. So far, I've been very happy with this setup. It seems more than adequately secure (even without the Loctite) as well as being cost-effective.
Make sure all of your parts and connections are solid as these setups are used at your own risk.