Thank You for the response. I aim to try out the cabana for a period, knowing it is not rain resistant, and in that anticipation looking for rain diversion hence the question regarding the "carport". I can only hope/experiment with it attached to the back rail of the Yakima bar over arching the cabana to shed rain ( driven rain is another issue ) off the vehicle.
The tailgate enclosure in my photos is a modified DAK 'midsize campertop tent'. I did not have problems with rain, but it isn't as bug proof as I'd like (mainly around the car sides). On top it's the tailgate that keeps rain away, the enclosure just keeps it away from the sides. I do get pooling in the trough between raised tailgate and car roof, and have to keep that in mind when taking the tent off.
However I haven't used that tent enclosure in some time, since I realized that I had plenty of sleeping space inside the car with the tailgate closed (that's with platform and lowered front seat backs). In cool rainy PNW weather I don't need the extra ventilation. Occasionally I have rigged a mesh screen over the partially open tailgate opening, or in buggy conditions switched to tent which is easier to keep bug free.
I've tried various tarps over the tailgate, but have been happiest with them over the side of the car. I've used the Vista tarp more than the Carport.