I did not set the records - RIB Unlimited did and a friend of mine was a part in designing and building the boats. I just told the history of the boats as they probably are not very common in the UK.
My boat is not for the very rough stuff as you pointed out but I live quite a bit in (10km or so) a fjord. I use my boat for going to beaches in the archipelago, restaurants and the odd excursion along the coast (mostly inshore)... and also for some joy rides when I want to go fast (70mph is relatively fast as my previous boat did about 100mph - Allison SS-2000).
I bought this RIB Unlimited to rescue a quite rare engine - the Mercury ProMax 150 ss (2.5 efi short shaft sport master - 150hp race engine). I helped the first owner in Sweden find it on the Allison Owners forum in the US... 187hp in a dyno and the boat is CE for 115hp.
I have had to re-do the setup with a CMC hydraulic jack plate, a SeaStar Tournament series hydraulic steering, T-H Marine hot foot throttle, SeaStar Pro Trim (for the trim and the jack plate) and SeaStar Control to shift gears. I have also put in new wiring with Argent instrumentation (tacho, fuel, trim, water pressure and volt). I now run a Mercury Trophy Plus 25p four blade propeller so it accelerates quite hard but is very pleasant to drive. I also have a Hoss Triton I - a real challenge so I don't run it. I am done with chasing speed so I have a good, safe, allround and fun boat. Ok, perhaps not for the beginner but I have been into both offshore racing and extreme sport boats for many years.