Desperation has set in. The Dampervan doesn't float and if the project can succeed that's precisely what it must do. I pondered adding some air-tight boxes to the underside to raise it up in the water, and then realised that some more polystyrene would work just as well and be a whole lot quicker to apply. Anyway, if it worked I could do a proper job later.
A slab under the middle of the van plus a couple of blocks at the back end were stuck in place with suitable solvent-free glue. Once dry, the van was launched again.
This time the waterline was very nearly there. OK, so the back is still a bit saggy but the front could be weighed down a touch with the mechanical bits. On some real water it might even be acceptable.
But at what cost ? To get the model this high on the water I've had to stick great chunks of polystyrene underneath it. To make a practical model, even bigger lumps are really required. On dry land it no longer looks like the prototype damper. The compromises and disfigurement to get this far are huge. Too big for me I think.
The problem is fundamental. I had assumed that because plastic floats, a plastic camper van would float. In reality, the kit is just too heavy to be seaworthy. That's not the manufacturers fault, they didn't intend to make a boat after all. If I want to build a working model of this vehicle, it will take far more work than the "quickie" project I'd originally intended this model to be. Therefore I need to move on and do something else. Unless some fancies taking this on (and if you do, drop me a line) I'll pack the model up and one day it will re-appear as a static item. The modifications so far look OK so this should work out but it won't be nearly as much fun.