: All the way forward, about 10" from the trailer's front wall. Where the axle is, and where the bike will be will end up with the bike over the axle, with the weight slightly forward. If it's a V-nose, you want the tip of the front tire at the line on the floor, prior to entering the "V", so the chock isn't mounted in the "V" part. When mounting the chock, look under the trailer and try to get the two most forward bolts through a floor support, for more strength. If not, use large washers un the underside to create more strength when mounted to the floor. I used 2" washers.
: 4, one in each corner, and as close to the front or rear of the bike's outward tire tip as you can, so the tie-off points are at an angle, and move slightly outward from the bike, and not straight up and down. It makes it more stable, and easier to handle the bike when disconnecting the tie straps.
Don't cheap-out on the wratcheting straps either. You get what you pay for and there's nothing worse then opening the trailer door and seeing a failed strap and about $1500 in damage due to a bike that came up hooked....
If you can, look at E-track, as that allows for movement and placement of D-rings anywhere you want. You screw the E-track down, making the trailer more "bike friendly" to more then just one bike, or vehicle for that matter. It mounts to the floor and allows for straps, or strap ringd to "clip in" to it and can be easilly moved. I ended up adding that to mine, after the hoops you see in each corner.
My enclosed trailer, before I sold it...