I've got a pretty good handle on what was going on and while the HK will shoot a tiny bit lower than the 1911 for the same picture, the low shots are more the result of a sloppy support hand. When I'm late with my support hand I tend to get a sympathetic squeeze out of my lower three fingers which dips the gun. The results are less pronounced with the heavier 1911 which also provides a bit more purchase for even a sloppy support hand.

What am I doing to fix this?
  1. Really concentrating on support hand grip with more draws at reduced speed
  2. Getting my support hand on the gun sooner to avoid having to catch up
  3. Working hard on transition from target focus to sight focus as I drive the gun out
  4. Installed the larger grip on my HK P2000 and purchased a P30SK for deeper concealment and with even a greater ability to tailor the grip features than found on the P2000

I noticed a big difference today on the quality of my sight picture as I was breaking the shot just by having a good two hand grip early in the draw cycle. I know this seems obvious, but you develop bad habits. One advantage to the Idaho winter is my wife and I have been practicing at an indoor range which allows holster use and imposes no rate of fire limitation. This has allowed for the sort of introspection that is hard to come by when you're essentially shooting stages 2x/week. April is around the corner which is the start of steel challenge season in these parts. Of course this carries over to defensive use of my HK.