Bjorn, the Stalwart is empty, they will swim with 5.5 tons but it best to keep them to 4 tons. I don't have the swim board on the front, it's in the garage, but the nose does truck under a bit at speed and the bow wave moves up the windshield. The crane models FV623 & FV624, sit decidedly bow down when unloaded. They go about 7 knots under jet drive and 3-4 under 4 gear tire propulsion. With the jet drives engaged they are supremely maneuverable, turning in place or backing with precision, trim can be further accomplished with a slight turning of the steering wheel letting the tires act as rudders.
All that said, it is still a truck not a boat, it does have the benefit of having a hull though. The funny thing is it has a double "v" hull that provides some ballistic mine protection like the newest armored stuff being sent to Afghanistan. Stalwarts were capable of having one or more wheel stations blasted off and still carrying on the mission.
You'd be the perfect owner of one, passionate enough to keep it maintained. I'm not trying to sell you one of mine, we are just too far apart to make ANY economic sense whatsoever.
Sorry for the thread jacking, it is another 5 ton amphibian