If your 23.5 is anything like my '98 240, then there should be an aluminum backing plate molded into the fiberglass under the channel. Again, assuming that the boats are very similar in the bow. I had a 1/4" thick piece of wood that served as a divider at the forward end of the V-berth. There were two screws in the lower corners of this divider and it was caulked into place. If you will carefully remove it, you should be able to contort yourself enough to see the underside of the channel.
I drilled through the plate and then used a tap to thread my holes, bought bolts long enough to go all the way through the plate and then used washers and lock nuts on the back side. I also put down a healthy coating of 3M sealant under the roller (can't remember if I used 5200 or 4200) to keep water from working it's way underneath and utlimately into the cabin.
Good Luck and Fair Winds,
WTA
