How to switch Golden Tube Audio SE-40 to mono mode

How to switch GTA SE-40 stereo amp to mono mode operation?
Don't have a schematci. I do see jumpers on the bottom of the circuit board but no intrusction. Please help.
Don't own this amp myself, but friend does. We had it open for rebiasing and he showed me the small jumper to make them monoblocks. It's right in the center when you open them up. It's a wee-tiny little jumper that's probably sitting across one pin, leaving others exposed. It should be covering all pins to convert to a monoblock.

HOWEVER - BEFORE YOU TRY THIS - please talk to a dealer or to the manufacturer directly. Again, I don't own this amp and am working from memory.

If you still need this info I have the user manual and can email you a scanned copy if you like.