In the original question, turftime was asking about performance/engineering, and most of what I was getting at revolved around that. I agree with what everyone is saying about redundance/safety with twins, (to a point), but I was addressing the question of performance/engineering. If I am going out so far in a boat that I think I needed twins, it sure isn't going to be in an open 23' boat.
Specifically regarding twins, if you can't get up on plane, and can only run 8-10 mph, IMHO, your better off with a 20 horse kicker with a nearly flat pitch prop. It will get you in at 8-10 mph, weighs alot less, and cost a whole lot less. If speed is what your after, well, than, go with triples
The "bathtub" brackets like the hermco are really only turning a 23' boat into a 27' boat. This is a pretty radical change, and I haven't been on one with a hermco with twins, so I don't know how they work. I know guys that have used armstrongs and DnD brackets with twins on a 23, and most, if they had to do it over again, would of gone with a single 300. It's not that it's terrible, but in ugly seas, where you have to run slow, in the 20's, the balance is screwed up, and they tend to be nose happy and stern heavy, especially in following seas. These boats, like most deep V's really aren't at their best in following seas. Too much weight in too short of boat, for the most part. Remember, the original design spec was for 2 motors that weight about 100 pounds more than a single current 200hp. On flat days, well everything rides good on those days.