Welcome to ModelEngineMaker !If you have problems registering or logging in, please use the contact menu option to request assistance.
... I don't see any real reason for not drilling the holes all the way through ... ball bearings works best with an oil mist to lube them no mention of it being mixed with fuel
I have long considered the big version of the Kinner K5 from SIC. but haven't made any movement on itArt
This view shows the approximate oil level based on recommended fill up volume. Notice how the bottom set of tappets (cam followers) would always be submerged in oil. I envision even medium viscosity oil working its way out through the annulus gap between the cylindrical tappet & the bronze bushing ID hole. The tappets are sliding fit & perpetually moving up & down. So possibly even some light pumping action. Maybe any bypass oil volume is minimal & just migrates down the pushrod tube where it ends up in the lower covers. I’m not really sure. Obviously it must work because it’s common to the larger O9