I kept in place the two side boards that align the keel. I had to raise them and move them in a bit, but I have had no more trouble getting the boat lined up than I did before the modification. When there is a crosswind it is going to be difficult no matter what. Slinging the old bottom board under the trailer's cross-members is a big help because I can walk around on the rear end of the trailer very easily to get things lined up (I wear hip boots in colder weather). I also installed walking boards on each side near the front of the trailer. That being said, if there is a strong cross-wind I will still probably end up having to get wet and get help to recover the boat. (On days like that I either stay home or try to find a ramp that points down wind.)
Installing the rollers and raising the keel-trough sides is covered in detail in my previous post: "Modifications to Trailex Trailer." I posted it before I added the walking boards though.
You might also want to look at Pete McCrary's post, "Trailer setup . . ." for some ideas. He has made some pretty elaborate changes, including wedges to guide the keel at the rear of the trailer and at each bunk support. His ideas would work just as well with the keel rollers. I myself am loathe to attach too many steel fittings to an aluminum trailer though--too many places for corrosion to set in.
After writing this post, I went out and took some pictures that I hope will clarify the "walking boards."
Rear walking board viewed from the port side.
Rear walking board viewed from rear on the port side.
Front walking boards. The bungee is helping to hold a tarp covering in place. I probably should have removed it while shooting pictures. As you can see, Pete's design is much more elaborate than mine.