We now have our new 300 litre petrol fuel bladder tank installed under the port settee in the saloon, as pictured below. You can see the gravity feed pipe on the original tanks to the right, where fuel is fed into these original tanks and onto the engines.
I needed to protect the bladder from the obtrusive bolts that hold the midsection of the boat to the port hull. I covered these with plastic U section conduit and the entire port side of the locker with foam, the floor and Stb side of the locker have carpet and there is foam fore and aft. The breather is at the forard end going up through the battery locker through into the port deck locker where it ends in a a double loop.