I don't think the Akula tank will have enough volume to get a scale waterline on the Trafalgar, and the drive may not be well matched either. The propulsors are about the same size on the Vanguard and Trafalgar because of the latter's larger scale. However the pitch and blade area is quite a bit higher on the Trafalgars propulsor, so it'll load the motor more but I think you'll be okay with the MFA geared 500 motor. Personally with a Trafalgar, I would be tempted to ditch the propulsor, as the first of the fleet wasn't fitted with one until later in her career. A more conventional prop works a lot better, with no fixed shroud to muck up the turning radius, and less blades.
I'm not sure what the tank size is in the Trafalgar, you could have a word with Alistair, he has a Sheerline Trafalgar, unless he's sold it on.
The earlier Trafalgar hulls were heavily laid up hull, Chris Cloke modified later hulls and thinned out the upper half to help improve the boats stability. You can tell which one you have by looking at the underside of the top half, if it has strengthening ribs moulded in, you have the later hull. The ribs are there to help prevent the thinner laminate distorting.
Ramesh has one of the earlier hulls, with a lot of enhancements (new shroud, sail and hydroplanes) that were incorporated by U.S based modeller Steve Reichmuth. As such, I think it probably holds the record for most widely travelled model Trafalgar class, having gone from the UK to the U.S, then to France and back to the UK again! It has a scratchbuilt WTC that is fitted out with a pair of proportionally controlled Engel tanks. Works really well, although Ramesh felt performance was a little ponderous for his tastes.