my flooding hull is blocked off, The elephant trunks are well under water when at rest. i couldnt say exactly how much, beacuse last time i looked over the transom at rest two of us were right in the back of the boat trying to pump water out, and our combined weight made it pour in over the transom
but when i had one leaking the boat would fill with water.
At guess i would say if you left one down you may end up with 4" or more in the boat depending on how much fuel you have on board.
i will have a look next time its in the water, if you havent found out by then.
I think the answer is trunks up and a bilge pump.