I did mention this before, but I will again. The 3 things I would absolutely get right at the beginning are:
1) 3rd function valve. I didn't and had to pay extra to get it added later. That included a pickup, install and delivery charge. Definitely a miss on my part.
2) 2 inch wheel spacers. Before I got mine installed, I got the "pucker factor" on slopes that I didn't even think were steep. I can't really explain what that feels like, but as soon as you feel it, you won't forget it. Now I go on those same slopes and I don't even flinch. I feel planted to the ground.
3) Wheel weights. As mentioned, I didn't get them for the traction. The 600 lb backhoe gives me plenty of that. What they do give me is stability. Just as above, you want as much weight, as low to the ground that you can get. That helps lower the center of gravity. You have to remember that backhoe, while heavy, sticks up in the air quite a bit and moves the center of gravity. The weights help lower that. Plus, if you ever remove the BH, you will lose that weight back there. Without something, the FEL wont be able to pick up much before you rear tires are barely on the ground.