Sounds like a good plan to me. Besides, while you're in CA you'll be driving at the legal speed limit for towing. 

The reason aerodynamicists separate A and Cd is so they have separate shape and scale factors.  That way they can do small scale wind tunnel testing of a shape and then scale it up to full size using the frontal area A. 

Since the tow vehicle and trailer share an air stream they effect each other, so, think of the rig as a single shape, It doesn't work to try to calculate their areas and drag coefficients separately. In this case the rig has a frontal area of say 55 square feet, the area of the trailer, which is larger than the tow vehicle. 

We don't know what the Cd is, which is why the manufacturer's 55 square foot restriction seems pretty bogus. The other reason is that just slowing down 5 mph has about the same impact as say the difference between 45 and 55 square feet would, everything else being equal.  My guess is that the manufacturers just use A because it is fairly easy to measure. No one knows the Cd of each combination of tow vehicle and trailer. It allows them to place some kind of limit on the size of trailers being towed which they could use to protect themselves from litigation I suppose. 

I came up with the roughly 0.4 Cd for my rig by backing into it using fuel efficiency and rolling resistance numbers. But its a rough assumption, and similar to what other boxy vehicles are. The way to find out would be to do coast down testing. For me, that would only be worthwhile to test out the effect of a spoiler on the back of the SUV or removing the a/c or something like that.

Good for you in recognizing that the tow vehicle you have isn't up to towing that trailer. You have a decision to make, smaller trailer or bigger tow vehicle. I have a Highlander which is a good all around mid sized SUV with I think the same towing capacity as your Pilot. It gets used 90% of the time with no trailer behind it. Paired with the 179, it is a good match and provides what my wife and I find is an ideal size rig for two people.  I wouldn't want anything bigger, and wasn't interested in owning a pickup truck again. Others have different needs, opinions, and budgets.

Thank you all for the info! Lots to consider. 

I guess it works well as we just got back from another trip to the Lassen National Forest and the truck's computer says we got 14.8 mpg.  I wonder if it's lying or trying to trick me?  I think we'll go camping again at least once more in July, and as many trips as we can squeeze in in August and September.  

Excuse me, but speak for yourself  At least 3 people on this thread both understand the formula and are interested in the frontal area and drag coefficients of these trailers, and in why the manufacturers spec them as they do. If you aren't interested or choose not to take the effort to understand this stuff than that's your choice, just ignore the posts. 

As for leading to different conclusions by everybody, that does not seem to be the case. I for one happen to agree with you, as I have said. A Ranger with the higher tow rating should be able to handle a 193.  

Maybe it would be useful for RV manufacturers to publish the flat plate frontal area?

Thanks for the explanation on how to calculate the frontal area. I've not seen that before. I'm sure there is some computer program somewhere that essentially does the same thing.

Edit: I did a quick search and found this:

This one is simpler if one can find transparent graph paper:

If you really want to know your frontal area more accurately, here's the old school way. Cut out a 1 foot square piece of cardboard and tape it to the front of the trailer. Stand way back and take a photo. Then, blow up the trailer section of the photo and print out the photo and little squares the size of the cardboard square. Cover the whole trailer with little squares (and parts of squares) and count them.

Frontal area only effects air drag so is only going to be an issue if you are a speed demon on the freeway. Drive slow and it will never cause a problem.

For the same reason I think engine horsepower is overstated as a towing concern too. The 2 1/2 ton 6x6 truck won us WW2 towing unbelievable loads and it only had a little over 100 hp. But it was constructed to handle heavy loads, had very low gearing, great traction, a reliable engine and a good cooling system.  It just went slow is all. 

So if the Ranger can handle the trailer load and tongue weight, the weight of the stuff and passengers in the truck itself (MCGVR greater than actual loaded rig weight) you should be fine. Just don't speed. 

Please post all your trip reports, impressions, and notes here so we can follow along!  I've never seen one in person so I'd love your thoughts on it.  I saw a question upthread about the comfort of the Murphy bed, and I'm also wondering whether you feel there's enough counter space to make the kitchen functional. 

That is mentioned in Ford's towing guide for the Ranger. See this link:

Personally, I think the frontal area is a bit too restrictive. You should be fine. Just be aware that it will impact your mileage and you will be okay. I can't even find anything about frontal area limits for the Frontier in Nissan's towing guide.

I'll have to look at the Frontier.