I am going thru the same ordeal. I have begun to consider converting my trailer to a gooseneck hitch as it will give me the adjustment in height. From what I can figure is that the trailer needs to go down the road level or as level as possible. In order for my trailer to ride level it would need to be riding at 49" hitch from the ground to the bottom of the kingpin. I have then measured the distance from the ground to the top of the truck frame which is 33"   Therefore my leftover distance that I have to work with is 16" which is the height of my Reese 16k sliding hitch. Which means for my trailer to ride level I have to install my sliding hitch on the rails which leaves me no room for my bed therefore I'm considering switching it over to a gooseneck which will give me the height adjustment but it will take away my load slide capabilities which from what I've seen is not that big a deal. Also be sure to measure back from a any place a trailer might turn into ( i.e. Your welding machine) back about 4'6" so that you can turn 90 degrees and not turn into anything on your truck. I came up with 4'6" by diclviding the width of your trailer in half and adding a few inches. Hope this helps. Also if contact me if your interested in my sliding hitch as I am probably not going to use it. I'm currently working in NE Pa near Towanda.

Mount a B&W turn over in your bed then you can use fifth wheel or gooseneck. Also the receiver for the ball can be used to mount a pull out burning table umbrella or a swing out fab table. Just buy the center section and fab up the rest yourself. You also won't have to deal with rails if you slid stuff up on the deck it will be smooth.