I'm assuming it's a dual axle trailer if 14'. You could easily mount the compressor against the front wall. The average hot water pressure washer weighs over 900 lbs and nearly everyone puts them at the front. Then center your 240 gal tank and 2 70's over the axles. Are you mainly going to be doing roofs? If so, why the big water tank? I think you may find that a 70gal mix tank is pretty small. That's one decent size house. If you look at some pics of some of the other rigs on here you'll see that many have a 200 gal + tanks if they're doing mainly roofs. As far as an SH tank, what I quickly found out was it was a lot quicker and easier to just load the barrels onto my trailer, other wise you're pumping them twice, once to fill up tank and then again to mix tank. I simply pump out of the barrels over to my mix tank. With your enclosed trailer probably easiest place to load would be in your side door, depending on your SH supplier.