Atokatim;
Let's do a little bit of detective work here. I think we need a little bit more info.
First, you have a double-wide mobile home, you have a tin roof about 1/2inches above the original roof .
Now what kind of better efficiency are you looking for? Lower cooling bills? Lower heating bills?
IF it's lower cooling bills, then here's what I did in my brick home up is St Louis, MO that has had a noticeable improvement (improvement being that instead of a $150/month AC bill it was only $90) . IF you have access to those cute little 100 and 120mm DC power fans for free , get as many of them as possible ( I used 16 120mm in total) . Wire them in parallel , mount them at each of the attic gables to push the attic air out, make sure you have access to air from either outside or inside the house so the fans have air to work with. This will move the heated air out of the attic thus helping your cooling efficiency.
Another one would be to try doing the same thing for the tin roof. Tin once heated up by the sun will heat the roof below it , again causing heat to be transferred into the living space.
IF it heating you're looking to make more efficient , then let us know.
Hope this helps a little
Bruce S