Would this work on a Com-Pac, such as my Horizon Day Cat?
Rob
http://www.jamestowndistributors.com/userportal/show_product.do?pid=98161&familyName=TotalBoat+Trailer-Mounted+Boat+Lift#MyReviewHeader
It very well could dependant on the trailer build.
I like these, look like they are made by brownell, but I would make a suggestion, if you get them and have to extend them in or out far (that is the side adjustment), be sure to block the pipe that sticks down, block under that so that the pressure is less on the trailer.
I might be looking into this system to see what I can do with mine, as I now no longer have a lift to freely use anymore.
Mac
There are a few posts on here on how to lift the boat with jacks. Look them up, much cheaper!