[willy]

Depending on engine/hull condition with a 150 you are looking at between 38-44 mph loaded up.
The 225 two stroke I drove made 45-47 mph on gps smooth water and trimmed up, full tank and three guys and enclosure up.
Greatly diminishing returns with these hulls above 150 hp. lot of fuel expense and weight on back of transom for little gain above 150. This is especially true with a four stroke above 150.
the ETEC gives you more power to weight so would be better, in the 175 - 200 hp range.
A bracket adds performance with a smaller engine you would get going with another larger engine. With a slight loss of manueverablity. And the larger engines on the brackets effect ride quality and will cause your stern to sit low in the water often below the scuppers, and you have to watch coming off of plane to abruptly as you can come close to giving your engine a dunking.