Haven't been to the sight here in awhile. You surely do have it fortified. Never hurts to go that extra mile, lol. I did the same when I built my Personal Training Studio. The Inspector told me the foundation would hold a dump truck, but having 22 Cybex, Nautilus and other machines, not to mention a full set of dumbbells and cardio I wanted to walk that extra mile. I loved the North when I could play in the cold. I took many ski charters up to the Porcupines and Indianhead Mts. in upper Michigan. You probably have heard of those, but now my bones like the warmth and here we have the best average temp. of anywhere in the USA so they say. A little hot in the summer, but I can take anything up to 100. On your slab, if your not going 6"s you made a good choice for piers also. Down here they put these floating slabs in the resident homes. Not thick enough and never let them cure like they should before putting weight on them and right over all the plumbing and with no piers (at least not in mine). I had to hire a foundation co. to level my floors before I could sell it. When you do that then you have doors and windows, plumbing, electrical that need repair and even cracked walls and ceilings. I had minimum as they could have gone 100% level, but beings they did not it saved a lot of extra work and the buyers approved and so did the inspector and only cost me $6500. Yes, still a lot, but that with other repairs and Realtor Fee's it cost me $20000 to sell my house. Good thing it was paid for as I sold my Fitness Studio, House and custom show bike and bought this ranch. This is where I want to be till my time is up. Good luck in your quests. You can live anywhere, in anything if you have to. When the time is right, you change that. A piece of land with a barn like yours and a mobile home is a blessing believe me.