Mr ta2d,
I also own an HK Compact .45 with the LEM trigger, installed by the factory. I asked the factory to install the lowest trigger pull weight springs possible, and it came out at about 6.5 pounds. After the installation I sent pistol to Tommy Thacker of Thacker Guns to have the trigger pull weight lowered further and to have the action smoothed.
A problem indigenious to this particular pistol is if the trigger pull weight is lowered too much you run the risk of light hammer strikes causing misfires. This occured on my pistol when the trigger pull weight was lowered to approximately 5.5 pounds. One fix is to use ammunition that has softer primers such as Federal, but that was not an option for me. We had to replace the springs with the factory 'light' springs, bringing the trigger pull weight back up to a consistent 6.5 pounds. Tommy smoothed the action considerably, so the trigger FEELS much lighter than the Lyman Electronic scale says it is.
I'm not saying that your particular pistol will get the light hammer strikes, but I did want you to have a heads up. More information on this is available on the HK forum website at HKPRO.com.
ETA: For some reason, this problem does not occur on full size USPs or on Compact .45s that have the standard (non-LEM) trigger. This occurs only with the Compact .45 using the LEM trigger.
I really like the LEM Compact .45 and when I'm not carrying my 1911 this is the weapon I carry.
Mike