Thanks, Moggy.
According to a comment on my link, RTTL 2748 was at Plymouth being restored as of May 2008.
As I remember, they had 3 x Napier Sea Lion engines and could do about 33 knots flat out, with a whole lot of shaking going on, so it was a case of two hands for yourself, never mind one for the boat! The spec. says 24.25 knots, but I was assured by the crew that we reached 33 knots on several occasions.
This spec shows the dimensions:
http://www.asrmcs-club.com/BoatsWebsite/rttl1aspec.html