You didn't provide any cargo data but you have indicated all along you like boattails. Boattails in that configuration (not hanging off the rear as extra length) don't mix well with large interior volume requirements. You see, that is the reason I asked those questions.
If pulling a box trailer, a boat-tailed pickup cap is not going to provide the best aero. If not pulling a box trailer, a boat-tailed cap is what you want. A boat-tailed cap would also work well with a flat-bed trailer with low, heavy loads like a stack of steel I-beams, for example.
But I'm just shooting in the dark here yet because the function remains undefined.
A gaslog is practically a requirement too.
As far as the Rivi ad and aero: advertisements are not a good source for factual information.