Re: Which is worse, a CAT that has some hull slap or Mono rolling on the hook?
"hull slap" on a Gemini is an issue only in choppy confused water.
The stern under the cockpit is about 10 inches above the water, a following wave can 'slap it'. The bow of course slowly slopes down from 38 or so inches to that 10 inch level, a confused sea can slap it as well.
Generally, not so much. Never a constant thing wave after wave.
Now water over the bow, same story, only if you are speeding along in chop (4 footers) with a period (distance) between waves that has you plowing into a wave while your stern is rising on the last wave.
At anchor, steady and good sleeping. Nice big open cockpit for socializing.
Do not over load the boat with weight, performance and ride are greatly affected.
Lessons learned are opportunities earned.