We carry our bikes on the rear hitch of the tow vehicle. This way there is no extra weight resting on the PC, and we can drive to the bike trails with the tow vehicle. The draw back is that we bring our bikes everywhere when driving our tow vehicle, unless we take them off and lock them up at the camp site.
We did the same, the first time I used my Ranger for a toad. When I checked my mileage at the end of the day, I discovered I was only getting 7 mpg over flat Texas land. I moved the bikes into the house for the trip back, and got 8 mpg on the way home. We carried the bikes on the RV hitch for years before we started dragging a toad and never noticed any impact to mileage, since the motorhome shielded the bikes. Of course, a pickup is the worst case, and we used a bike cover, but even so, not much of the bikes were exposed above the bed. I was surprised at the impact to mileage.
We finally bought a Smart car last year, and sold the E-bikes. We've only taken one trip with it, but we averaged 9.5mpg on that trip. I think it's so small that it's mostly in the shadow of the RV, like the bikes were.
