Side Skirts and Tails or undercarrage

I've got skirts on the Great Dane I pull and honestly think they cost me fuel mileage in high crosswinds.
Also not sure where to hang my tire chains this winter because they don't angle inward behind the dolly legs like others and can't make alterations until lease is paid off.
Would personally prefer the UT6 if I'd had the choice.

 

We have both in our fleet, talking to the drivers sounds like they make about the same difference. I know the UT6 are virtually indestructible, Ive got pictures on my work computer of a loaded trailer sitting on the undertray (tandems got backed into the ditch) when the wreckers pulled it out of the ditch the undertray popped back out to normal

 

I'm running the side skirts. Seeing a steady gain of roughly 0.3 mpg. I would add them to all my trailers if I owned more than one. Can't speak for the under tray system, have no experience there.

 

I can't say enough good things about skirts, but haven't tried UT6 or tail to say which is better.
I've seen gain as high as 1.5mpg but I'd guess avg closer to .5 - .7mpg w/ skirts only.
Allan M makes good point about hanging chains. <---something to consider

UT6 has claim of up to 10.5% savings, but don't mention what testing standard they used.
Transtex Skirt claims 7.4% using EPA SAE type II testing skirt only.
Transtex Tail claims 6.58% using EPA SAE type II testing tail only
Transtex combo up to 12% (seems realistic)

Either way, I'm sure which ever you choose will pay for itself.

 

The trailer came with them already installed so I can't answer that question.
iIt doesn't matter what type of trailer I pull though with my Cat engine the fuel mileage is never great.