Something to ponder.........
A twin engine'd RIB would typically (not exclusively) be 7mtr+ and would come in at over two tons including the trailer. Borderline and maybe OTT for a "mid sized" 2ltr 4x4.
I'd check your manufacturer's specs.
6.5mtr would do what you're talking about (once you've built up a bit of experience) and probably come within the towing spec of your car but there aren't many 6.5s with twins. More likely main +aux.
I've done the trip from Dublin. (Skerries) to Dumbarton and I certainly got a "buzz" from that but even locally there's so much up that east coast of Ireland that'll keep you occupied for a long time.