Before you buy a sit in kayak for paddling from a boat, I suggest you try getting in one in choppy conditions from a boat. It can be done, and I have done it on supported trips where the boat drops you off, but when we do this when surfing we just seal launch from the deck. Probably not something you want to do if you are worrying about getting stuff wet.
I would post on www.sit-on-topkayaking.com, there are a few folks there with experience on using kayaks from their boats. IF the Frenzy is too small, and I really doubt it for what you want to do, look at the Ocean Kayak Scrambler .... we actually see a lot of these tied on to boats here.
Cartop Kayak Carriers
Kayak & Canoe Outriggers
PFD's (Life Jackets)
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