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Tor as you haven't changed the injectors doing the PI/DI separately is probably not worth the effort. The issue is that the DI fuel system runs at different pressures when fully used to when switched off so you can't tune it for just fully on or fully off. The PIs are also the limiting factor, not DI.
4.2/4.25v would work as the MaxV, I leave the OEM minimum and the min unchanged should be the lowest voltage you see.
As for zeroing things out, you could do the ELC but it's not necessary. You'll just reverse the normal compensations but they might make things more accurate as they are. You could also do the same or not for IATs. I now calculate a new ELC table using the same data as adjusting the MAF, kills 2 birds with one stone.
Also, if you're really that bothered about the MAF, set all your open loop fuel target to one value in the region of 12.5-13 and that way you're not chasing a changing fuel target.