i've posted this very question on at least two occasions. my goal was to launch and retrieve on my own. i had two concerns regarding attaching a ladder direct to the bow, one, didn't want to drill holes in the bow and two, didn't want to deal with storage of a rigid ladder. what i ended up with was a 4 step rope ladder, worked great, easily stored. i secured it to the center bow cleat, dropped over the side and that was it.
now that i have a different boat i'm faced with the same original problem. so, when i pulled the boat at the end of this season i'm going to deliver it to a local light machine shop that has agreed to fabricate a ladder which will be attached to the trailer.
good luck and let us know what you end up with.
pat