Yamaha DTXpress/DTXplorer/DTXtreme

I'm nearing completion of my DTXpressII kit editor but I've hit a 
problem which is looking like a bug in either the sysex 
documentation or the unit's operating software.  If anyone here has 
any ideas to offer, or a contact at Yamaha they can send my question 
to, I'd appreciate it.

Basically, I am using the Parameter Change Sysex message to edit the 
kit and have no trouble getting the unit to respond correctly to 
everything except the Song Tempo under KIT COMMON.  If I send 
Parameter Number (8 8 - -) I have no problem selecting the song.  
However, the two Tempo Parameter Change messages do not appear to 
work.

Parameter Number (8 9 - - ), which should set Tempo MSB, appears to 
do nothing while Parameter Number (8 10 - -), LSB, always resets the 
Tempo to --- no matter what the value of the data byte sent.

Anyone got the experience or contacts to solve this one?

Thanks,

Peter