I bought one of those "Shelter" logic tent garages for my truck. Now that I have it I see it needs some things to help it keep the truck dry. In this climate (Pacific North West) the moisture in the air condensates on the inside roof and drips down on the truck so it is mostly wet. Not the end goal here.
The plan is to cut a hole on either end and install a solar fan to help move some air and dry it out. However in the mean time I hatched another plan.
Double wall the thing. I just so happen to have an old plastic bag from a queen size bed and the plastic is thicker and clear so one can see the result of the experiment. I installed it the other day so it sort of hangs below the outside covering and held it away from the truck with sting. So far so good, the first drop has been kept from the truck.
The solar fan will come when I find one on sale.

I also thought this thread could be where others give opinions of the tents they own.

I also own a 7 year old smaller S. Logic unit for the back yard stuff. The top lasted 3 years and then the sun had done it's job and it needed a new top. I bought a tarp which was crap and now have a vinyl tarp on it for just over a year. Will have to see how it continues. The frame itself is just fine and both ends have lasted the 7 years but now need replacement.

 

stuff is not made like they use too. i had one of them 25 years ago . i used to set it up every fall as a hunting camp. it was 10x20 would heat great with a wood stove, but you need a double canvas for condensation. we would sleep up to 4 guys in it. then i would use it home as a car shelter. i bought it second hand ,had it apart and together twice a year. gave it to my father like 10 years ago ,he used it for atleast 5 years permenently installed . then he built a garage!

 

So after some time with the old plastic bed bag hanging off the inside pipe the jury is in.
The double glazed principle works! The truck is dry and I have bought two cheap white tarps and modified them to hang under the pipe frame. It may not be the most professional job but it does the job.
I installed it in a rain storm and noticed that the condensation on the inside would form droplets and when a big rain drop hit it would punch the inside drop off and onto the truck. Actually saw this happen (the drop may have come from the power line above but still) as I was standing on the flat deck putting up the tarp when the drop got me in the eye. I happened to be looking right at it and it did not drip off like other drops do when they get too big. A strange thing to witness.

 

Speaking from experience, most of the interior moisture is actually from the ground. If you cover the ground with thick plastic you'll cut out much of this. It's pretty humid here in the NE and we have particularly clayey soil here in upstate NY. Ive found that, with the exception of those annoying times of year when we go from -5*F to 45*F in 24 hours (e.g., this week!), most of the condensation on my outdoor-stored equipment was from soil moisture. I covered the ground in my equipment shed, added a gutter to the back, and the rust from condensation almost completely stopped. The interior of my metal roof was almost always covered in a film of water, particularly when the temperature changed drastically, but it never is now. Of course, ventilation as you suggest always helps

 

I have a second tent now that I put up on a gravel area in the back. As the professor said the ground is wicking up a lot of moisture and the inside is wet and dripping. I have not moved the truck and will wait till I get the ground covered. The plan is sand over the gravel, a heavy duty tarp, more sand then either gravel or bricks.
As for my first tent, that is sitting on my paved driveway I have had great success. It is like 95% dry and only gets some wetness from front, back and the edge where some cracks go all the way under the side wall. This summer I cleaned and then sealed the side wall to the driveway with some gutter sealant. I did a double pass along the bottom edge and then taped the edge as well to the driveway. I expect the tape to come off but so far this, as I mentioned, has worked very well.