Well if its really about big end lubrication-as measured by crankpin wear-[ovality or taper-take your pick] I think it is a combination of multiple things-we haven't yet brought bushed/unbushed rods into the discussion-and I'm not sure-short of the testing regime I mentioned earlier-which is largely impossible to create in practice(!) you can separate out the factors-other than to say that 'my engine builder friend claims that lubrication notches on the crankweb side of the bigend are superior based on wear measurements' to which I'd add:

i. based on measurements on .......... motors,
ii. of ......brand, and .........model
iii. used in ............event,
iv. after ...........hours running,
v. on..................fuel mix,
vi. on a ...............prop

Otherwise there's not a lot of rigour involved-yes 'xyz' amount of wear has been observed-but interpreting the reason for it is another matter.

ChrisM
'ffkiwi'

PS. One more to think about-and your oil galleries comment made me think-many plain bearing engines have an oilway stretching about 3/4 of the way daown the bearing lenth from the rear, to assist lubrication. In nearly 50 years of active aeromodelling-and having had 600 or so engines through my hands in that time-I've never ever seen a rod with this feature................................