It seems to me that It's unlikely that a small relief valve leakage will affect the operation under any but the most remote possibility so not likely likely to make any significant improvement. That said, no down side to if one feels like doing so....
As I have reviewed Paul's theory, work, and results my conclusion is that they, at the very least, do no harm. The leak rate on any given valve may be great or small, but it would seem that the small amount of work involved in stopping the leakage is time well spent. There's not much sense in having the pump merrily spinning away only to have some of the oil dumped straight back to the sump.
Tom, you commented regarding the bottom end being essentially like a two stroke and it certainly resembles those systems excepting for two factors which have been at the root of my concern from the outset:
1) The wrist pin does not have a bearing and runs directly in the steel of the connecting rod which means it requires both much more lubrication and cooling than a typical two stroke.
2) Piston cooling is highly dependent on oil spray from below onto the underside of the piston crown. None of us has been able to offer any means of evaluating the effects of reduced spray on piston cooling in this engine. IME, pistons reach a critical temperature after which they fail in a rapid progression.
Yet there is one notable condition that doesn't exist in a two-smoke and one notable observation.
The KLR has a sump and the environment in the crankcase is extremely oil-rich. In the event of a piston ring failure one can expect a tremendous amount of oil to be blown into the air box, as Trundlebike saw with his double land failure. The wrist pin has concerned me, too, but I honestly believe that there is a whole bunch of oil floating about in the crankcase that should be sufficient.
The underside of a typical KLR piston is typically very clean with no varnish. To me that indicates that there is no cooling problem in there. Paul hinted that he thinks that his improvement in fuel consumption might come from the piston being just a tad hotter and therefore contributing to more efficient combustion.
There are many not qualified/not measured factors involved such as oil flow, for example. No one has been able to offer data or calculations indicating the effects of cross drilling the banjo bolts, for example. It is not unlikely that the cross drilling had no material increase in oil flow because the size of the cross hole may not be a materially affecting factor. That the cross hole is at 90 degrees to the axial bore will cause significant restriction, for example.
We don't have any indication as to the relative restriction offered by the long axial passage in the banjo bolt. It is quite possible that the longer axial passage has so much more resistance to flow that the cross hole size is immaterial. Someone pointed this out a while ago, again.
We have no indication as to whether the banjo bolt is a restriction factor at all, given the length of the oil pipe, so it may be that our drilling of the cross holes in the banjo bolt has no real effect on oil flow.
One would need to set up a test jig in order to attempt to duplicate the pressure drop across the various parts of the system as a means to evaluate these effects. If one has an oil temperature, same oil, and pressure at both ends, one should be able to calculate the oil flow rate, Correct, someone? Anyone?
Unfortunately, what you request is too hard to accomplish. If all of this is Bachelor's thesis, your suggestions would be at the level of a PhD dissertation. One would need a decent flow meter or be willing to measure how far a stream of hot oil squirts, as well as some machined fixtures to set the oil tube in and some sort of pump to circulate the oil. Might want a heater, too. Were one to go to all that trouble, why not measure flow instead of calculating it?
All that I have to go on is empirical evidence from Paul's data, coupled with some marginally educated intuition.
When the oil hits the banjo it runs smack into the bolt, has to go around it, swirls around for a bit, and finally decides the path of least resistance is to gown the 1/16" diameter rabbit hole.
Stranger things have happened, but it would seem that increasing the hole to either a single .125" hole or double .125" hole would not reduce
As to the axial hole being restrictive, once the oil gets in there it would seem that it would be no more restrictive than the oil tube itself. They have the same inside diameter.
Sometimes all we have to go on, without going to unreasonable efforts, is "try it and see". Modify, test, observe, and report. Draw conclusions and see what they suggest you do next.