I have worked out nearly all the errors now. The single-channel problem was due to a broken down line mixer in my rig. The low output level must be somewhere between the output from PCB005 and the stereo output (i.e. in the mix amp) as all separate outputs have a very high output level :-)
As for the two missing sounds (hi-hat and crash cymbal), I DID partially break the PCB while trying to de-solder a socket (stupid, I know, and I promise I've learned my lesson: NEVER try to de-solder a $1 part if you may break a fully populated rare PCB... *sigh* - and I was very much aware of the risk beforehand, but it was late and I had misplaced the DIL socked).
Guess it should be possible to fix both errors shortly!
On another note - the sounds are rich and beautiful. Big thanks to Trevor Page and everyone else involved in creating the clone!