The specific question I asked was “How does your sleeve solution work with 42mm shells without requiring reducing internal diameter of the bearing cartridge to the point of being too small for 30mm spindles? Are the balls you use smaller than those used in standard 6806 bb30 cartridges?” I couldn't fathom that machining the races down would be a good idea, but, as you say, pick your poison. Hambini’s solution for BB30 shells, near as I can tell based on limited googling, is ensuring bearing cartridges meet very strict tolerances and then installing them correctly (retaining compound, the correct snap rings).
Yep, sounds right. I'd stick to regular BB30 bearings for now. If you ever have the opportunity to get a new bike or frame, stay away from BB30 (PF30 is better, allows for sleeves), BB86 (not compatible with 30mm spindles) and BB90 (not compatible with 30mm spindles or sleeves).
PF30 and BB386EVO (which is just a wider PF30) are the most broadly compatible press-fit shells. PF30 is more compatible than BB386EVO because it allows for narrow BB30-only cranks. However, you sacrifice a little bit of stiffness - especially with longer spindles where the journals (ie, where the bearings load the spindle) sit outside the frame shell. /rant