I have a similar leak on my '03 UC with over 80K on the clock. But mine is actually leaking from the rocker box on the rear cylinder. You may want to try to get an eyeball (mirror) in there to make sure that your leak is not coming from above. The good part of that would be that it is WAY easier to fix this problem (if that is what it is) then if the oil is leaking from the crankcase somewhere. That would be an odd leak since it would have to be a pressurized oil channel that goes between the two halves. Not sure that exists at that location in the case.
TQ