What speed to expect.

I'm sure that's a delivered or light ship weight or something.

 

My previous boat was based on a hull by the same company (marine projects)and weighed 4.6ton with 1/4 tank water and 1/2 tank of fuel and all our junk on board, this was weighed on the crane during a mid season repair lift out.
It did have much lighter engines though and smaller fuel tanks.
It makes me think 4.5-5.5 tons is fairly realistic with average fuel/water load, 8+ sounds way over to me.

 

Have you calculated the weight of the keel structure ? What is it, aluminium ?

 

It's stainless steel, not sure of thickness.

 

That would have cost a few quid, and may still be costing money dragging it along for the ride.

 

And of course to make any use of it I have to drag the beaching legs along for the ride too adding even more weight, if I use them once a year it'll be a miracle so better off without it.