A trick that I have seen on a few diesel conversion and Team Race diesels is to simply file a 'star' shape or cross on the big end eye of the rod closest to the crank web, this allows four points for the oil to get out once it has entered, and it gives a full flow through from the star points to the back of the rod.

It OK providing an oil entry point with a hole or a slit but its more important that it has a really good exit point and a 'star' shape, much like the much vaulted crank web grinding seen on RC cars, will act as an oil slinger flicking away what is coming out of the bearing.

In talks with some racing guys here in Oz, they reckon that the star alone is far better than any oil hole or slit with the rods lasing longer.
(I found it hard to get my head around it but the proof is in the pudding!)

Cheers.