[Frank Lee]

I'd put more effort into finding an alternative to using the roof carrier; if you come up with one then a roof rack delete is in order if you have one.

None of those other things- even all added together- is going to even come close to cancelling out the bad effects of a rooftop carrier.

What I did with Moon Unit was internet shop for hitches; for me nobody even came close to the good deal I got from U-Haul. Not only that, I brought my tools, work clothes, and a piece of cardboard to lay on to the U-Haul store and installed the hitch myself out in the parking lot, and it was a piece of cake. IIRC it was a little over $100 total.

Perhaps you can estimate the mileage hit you take with the rooftop carrier and multiply that over 35k to come up with how much you can spend on a hitch and hitch carrier and still break even. Of course, you will still have those items for use after the trip as well. And if you don't want them after the trip they should have a good bit of resale value left.

With a hitch carrier you even have the option of cloaking it- possibly with coroplast- into a faux boattail, where you'd have a shot at improving fe.