Thanks for your help Wayne (and others). My roof is maxed out with panels, that is my limiting factor. I've decided not to push for 4 7.6 and 1 3.6 but I think in the long run I'll be happier if I do go with four 7.6 instead of three 7.6 and one 3.8....even though I recognize it won't make a huge difference. If Tesla doesn't want to do that then I'll go with their recommendation. Thanks for helping!
It depends on your panels and your layout. I have 100% unobstructed south facing panels and my 13.2kW system is clipping significantly (for over 3 hours a day) even now in February with a 11.4 kW Solaredge inverter. If you have shaded or multiple panel orientations then your system may not clip at all.
I have a 7.68kW solar roof with a delta M8 8kW inverter. Could someone explain DC to AC ratio to me? Why would a system clip? I'm not sure what my ratio is, and if it matters in my case.
DC to AC ratio is the maximum AC power produced by the inverter, compared with the DC power produced by the solar panels. Clipping is when the inverter cannot convert all the power produced by the panels. A 340 W panel only produces 340 W under ideal conditions. Up here in the Seattle area that may happen for ~2 hours/day for 4 months of the year, IF there are no clouds. So, it is not necessary to have a 10 kW inverter for 9 kW of solar panels, since they will seldom produce more than 8 kW.
Your DC to AC ratio is less than 1 so your system will never clip. Although your inverter may not be operating at top efficency with the wattage your panels supply the difference is likely negligible. The advantage for you is that you can add more panels without needing a new inverter.