I have mine positioned in the front most two slots.
On a related note - I got my R1S in October and cross bars in November for the start of ski-season, along with the Yakama FatCat EVO 6 ski racks, and drove all winter with them installed. While I wasn’t sure what the level of efficiency loss...
I did mine through Qmerit and was very happy with the experience. Professional and efficient. I bought my charger direct from Rivian (It showed-up about a week befor my R1S). I did have almost a 150’ run of cable so they charged me the extended wiring / conduit run. I had a 60 AMP breaker...