This was my second experience with the Dupli-Color, and a good one again. I have used your warmed can method, especially during these Fall build-offs when temps are lower during the day. Works well.
The split cable will be interesting. Mechanically it should work fine, but the physics might be off unless somehow you get the length of the cables to be exactly the same. I know when it's used in the standard format, two hooked to the gyro pulling one from the brake, it's still critical to get the length adjusted just right at the gyro so it pulls evenly.
In my case, I will have two separate cables from one lever, so I will be able to adjust the tension on each one individually based on the pull distribution by the dual lever. I've never used this set up before either, so it will be an interesting challenge.