I run a 2000 1842 tunnel with stock Merc 3cyl 60HP & 4 blade prop. I run 32.5 loaded down with 10 year old, Brownings, 2 dogs, a limit of ducks, and my big boned hunting partner. I don't know if his weight or wind resistance causes me more loss of performance.
I have had 28 alligators and my BBHP and still got up on plane but had to run the bilge pump the entire way back.
All I know is the longer you go past 40 years of age, stability of the boat becomes more of a concern.
I could probably cut back on CFM sandwiches, that may help a bit also.