[Fourbtgait]

Hello everyone.
New to the forum though I have been lurking for months learning from different posts across a wide range of subjects.
Now I realize a pre-built cargo trailer is not the most efficient shape, better if I built my own, which I may still do.
But....
Tow vehicle is a 2014 Toyota 4runner, on highway at 65 mph about 22 mpg.
In town average 19 mpg.
Both figured by pencil.
I need a small camp trailer, though a teardrop is ummm cute, not the most efficient. Thoughts are a 5' x 10' cargo trailer. Tow vehicle is 6' wide, 6' tall. Thoughts are a 5' wide, flat front (I would install a front nose cone) would stay inside the vehicle drag better than a 6'. The wheels/fenders would stick out 4" each side, about 24" tall. If I kept the trailer not over 6' tall it would "fit" better into the slipstream. But the inside height would only be about 4' 6".
Question is, is there a formula I have missed in life to look at flat front drag area? Trailer above would only "show" the wheels/fenders beyond the tow vehicle. Yes, I realize the slip stream begins to come back together behind the tow vehicle.
A better size or usable space trailer would be 6' x 10' trailer, 7' 6" tall. But then extends past the vehicle about 12+ sq. ft. exposed vs. 1 sq. ft. of the smaller trailer.

Always before I had diesel pickups, large travel trailers or gooseneck horse trailers, never worried. Now, I do not want to go from 20 mpg down to 10/12 mpg with large frontal areas. I would be comfortable dropping from 22 mpg to say 18 mpg driving 55-60 mph.

Thoughts?