I am probably going to have to re-deck my boat in the near future and if I do, I was thinking of also modifying the tank from a high to low.

Does anybody have any typical measurements or photos so that I can make sure the volume remains the same?

What design have you got? Have you thought of deck stepping it at the same time? One of the reasons for the lower tank was to stiffen the boat up around the mast step and shrouds and if you put the lower tank in you will need to re-step the mast to the tank/centreboard height anyway.

Jeremy. It's a Phantom Kipper and I was thinking about the low tank to add a little more stiffness and better bouyancy as we have had a few problems with getting the water out when we capsize (although that could be the excess weight she has to carry!!). I wasn't thinking of deck stepping but it could always be an option later

Well if you lower the bow tank you are going to need to re-step the mast anyway and if you are replacing the deck it makes sense to do it all at once. It is not much more owrk to do it at the same time. It will also help the bouyancy as with the big tanks half of it remains above waterlevel after capsize and so is surplus.

Why do you have to restep the mast?

If you're ripping out the high tank and starting again, surely you can accommodate the hog step. The V part would just need to be slightly further forward connecting with a post between hog and deck but in front of the mast step.

In the 80's style rig the masts are not stepped on top of the tank anyway, they step on top of the centreboard case. Since there is no case structure going that far forward on a boat of that age it's an enormous job to convert it to a case step, much harder than going deck stepped.

Even if leaving the mast step where it is isn't quite as good as the 100% 80's way of doing things it's still a million times better than the old style high tank. The thing to remember is if you are putting it in to add stiffness it needs to be strong enough to do the job.

Leaving it in position is fine as long as you can get the correct volume in the tank when taking the V far enough forward so as not to obstruct the mast fittings etc. As far as it being easier to deck step that was exactly my point. If you are going to change the tank you may as well go the whole 9 yards.

As i said, no buoyancy will be lost - the mast doesn't sit on the tank anyway.