If you haven't bought already, check out ebay...I saved a lot of $$ by ordering my kit from there (8 5' tracks, 8 d-rings, 8 strapped d-rings, and 8 end caps for $140 shipped). The only place I found it locally was Tractor Supply, and they want $12 for a 2' section and $5 per d-ring.
I ran two strips down the outer edge of my trailer, 2' off of the walls...which put the tracks under the rzr tires, and allows me to put 2 quads side by side, and the tracks run directly under the center of them. I'm going to order another kit so I can run a strip along each wall, about 3' up for securing loads to the wall (grill, nitrogen bottle for filling tires, etc).
As for securing it down, I bought a cheap $30 stud finder, which worked really well to locate the center of the beams under the wood floor. My floor is 3/4" wood, so I used 3/4" long wood screws ever 3rd hole, and used 2" self-tapping metal screws to tie into each beam under the floor.
I will post a few pics later this evening of the setup.
*edit*
the seller on ebay is globalpartspro if anybody else is interested in picking some up.