Has anyone used a drive on snowmobile trailer?  Some of these have dual axles and they run a smaller tire that sits under the deck.  They have tie downs on the deck already and some have a "clamshell" type of cover?  not sure if the cover would be tall enough for a Mini, but I am guessing they may.  

Possibly something like this:
https://www.floeintl.com/aluminum-trailers/enclosed-trailers/

I have yet to trailer a car, so I have no experience, nor do I have a Mini - YET.  I do have a nice little VW Squareback that I am searching for a trailer for since the old air cooled would have a tough time going too far.  I am leaning toward enclosed as well.  We have an open and enclosed trailer at work and even though the enclosed is heavier, it is used more often simply to keep things clean.  Most of us also feel better about having the load enclosed since it is a bit more secure and less likely for something to shift, especially because of wind.  

Food for thought.  

for anyone else looking for a sometime-use trailer, for $350 this one seems pretty "low risk/ low investment"

https://forums.24hoursoflemons.com/viewtopic.php?id=35948

I guess i do have a lot to think about now especially going enclosed. Well we are moving to a place with more room for a trailer and so I figure Id go get one finally. I don’t think im going for a single axle because of emergency reasons.

Just sold my 24ft TPD box trailer and bought a 2 axle open 20ft one. The box was nice but heavy and I couldnt fit some of the larger cars I move around in it (lack of headroom). Just make sure that the weight of trailer and car doesn't exceed the capacity of your tow vehicle with or without trailer brakes. pulling a heavy trailer is not usually an issue it's stopping the damn thing that causes the problem...............

After years of towing an open trailer, single axle,  now sold, I am getting an enclosed trailer, 7x14', twin axle.  Will carry any of our small cars just fine, and they will come out clean, with room to spare inside for tables, chairs, spares, etc...

Can't disagree with you, Al. Admittedly, I'm more Private Marginal than I am Captn Overkill.

I've towed Minis all over the US with a single axle trailer and have never had any damaged cars. Yeah, I've had tires blow out and still never worried about losing the trailer or the car. I think the key to it all is getting your weight distribution correct and don't try to run above and beyond the speed limits. Typically I drive 60 - 65 mph, except in sunny California where every trailer is forced to run at 55 mph or less. Also, I am so familiar with the feel of my trailer behind me I notice when something like a tire that is low or the load is shifting from a lose strap, etc. So, drive like you have some sense and pay attention to how everything feels.

Army ook, in your picture, the trailer has no fenders, a dirty car will be the result

Spank: I would always go for a tandem axle, better load carrying results and if you lose a tire you can get off the road

Now after years of towing with an open double trailer ( two minis) l have sold that trailer and only use an enclosed trailer, put the mini in clean, arrive at your destination and the mini is still clean

Big AL

i figured it’s overkill for the two axles but im just paranoid blowing a tire on the freeway and snapping a tie down cable if it falls on one side.

I’d get a Sloan flatbed trailer if budget wasn’t an issue. Really flat approach on a Sloan’s. We have a flat bed single axle landscaper that gate doubles as a ramp. Pretty useful except kinda hard to lock car down and has damaged air dams loading unloading 

double axle is overkill for a mini. Nice to certainly not necessary. I towed for many nears using a friend's solid axle motorcycle trailer that was modified by putting boards on it.

George, keep your mitts off of my trailer

It was custom made by a farmer who actually used it to tow double trailers. It too is overkill, a pain to back up because the axles are so far apart, but I've towed everyting on it from a stock toyota prius to 4 door jetta diesel, miatas, minis, a Ford Taunus, even a Borgward Isabella Coupe!

My favorite dream trailer is the Spank trailer. I love to get one, but I believe it’s custom made. 

https://flic.kr/p/21ff1aY