So just half throttle then. Good stuff, should pick up its heels once you get the trim dialled in right. Don't forget the FC16 has exponential, so you can dial in full negative expo and have 100% throttle, but the majority of the stick travel will be lower speed. That way you have the extra oomph on tap to get out of trouble, should you need it.
Trim wise, the spigot just below the upper rudder, which is the connection point for the towed array, should be just kissing the surface of the water, so you might get a way with a tad more weight at the back. It looks a bit low at the bow though.
Regarding a boat for your wife, have you looked at the Delfin from Norbert Bruggen? A little left field, and not a static diver like the Neptune, but what a lot of fun these look. Nice dimensions for smaller puddles. Bet you'll be fighting her for the sticks!
http://modelluboot.de/KITS/Delfin_Ordner/Delfin.htmlhttp://vimeo.com/26566825Norberts stuff isn't cheap, but it's very well designed, and the parts are good quality with straight forward assembly.
Bijou, propulsor technology was pioneered in the UK on the Trafalgar class, but has been adopted by the U.S, Russians and French, although their designs differ significantly in design to UK versions. Why aren't they used more? Well every country has it's own ideas on what constitutes good design, I guess some consider the disadvantages of propulsors outweigh the advantages. They do tend to place a lot of weight at the stern, which may not suit the smaller boats many navies use, and then there are the development costs to be absorbed. Also a fixed shroud hinders manoeuvrability, so not so great for boats engaged in littoral operations.