Draco- Good idea. I would have been worried about getting some metal shavings in the center of the bearing when the drill bit finally broke through.
How did you avoid this- magnetized drill bit?
Actually that's exactly what we did.
The mechanic put some rare earth magnets (which I happened to have around the house) on the side of the drill bit, before drilling, and didn't remove the magnets until after the drilling was done. As long as the magnets were in contact with the bit, the bit was magnetized very well.
I would think that if the bearings are in good condition there is little you will do to improve them. Keep in mind that when the bearings warmup the grease will thin down some and turn easier. You would most likely gain more by adding even just 1-2 psi to the tires, that is where most all of the rolling resistance is.
Sums it up nicely.
I would also add most people over lube bearings when they are serviced.
This not only wastes lube but add additional drag to the bearings.