The second option sounds better to me. Perhaps three 1.5MM holes directly behind the combustion chamber through the oiling groove. The oil lost to cooling is lost to the bearing no matter what.
You could drill three different sizes of hole, each set 120 degrees apart. Drill three holes in the bearing groove, slightly bigger than the largest cooling oil hole in the rotor. Grind off the alignment tab on the bearing.
Press the bearing in with the smallest set of spray holes lined up with the large holes in the bearing.
Test the engine with a temp sender in the drainback gallery in the center iron where all of the cooling oil returns to the pan. Run the engine hard with each set of holes lined up in turn, and compare the data.
Since you are feeding one less rotor bearing with the stock pump, I doubt that you will have any problem holding 80 to 100 PSI at speed. The engine will / may have poor oil pressure at low idle speeds, but this is not a problem as the bearing area is adequate for two engines. If you can get an indication of oil pressure, that is enough.
Lynn E. Hanover
In a message dated 4/7/2008 3:05:28 PM Pacific Daylight Time, lendich@optusnet.com.au writes:
The second option, and I'm not so sure it's a good idea, is to use the bearing lube hole and drill a 2mm hole in the rotor bearing through to the rotor cavity. Apparently this works well for delivering oil to cool the rotor, my concern is it starving the rotor bearing of it much needed lubricant?
George ( down under)