Thats what i thought initially, but reading between the lines he seems to be suggesting that the "external" tanks should have their valve (or the whole tank?) physically outside the vehicle, as he's talking about cutting a hole in the wheel well and avoiding ARB's...

My tank has its valve on the outside surface of the tank, but still inside the car.

Main difference between and internal and external tank is the way they are intended to be secured. You can have either a toroidal (with the multivalve in the empty centre of the tank) or a filled toroidal (which as there is no hole in the centre has to have the multivalve on the outside) intended for internal or external mounting. The tank you have could be mounted externally as it has the lugs all the way round for mounting straps.

Maybe a pic says more, this is how I did it:


Where the fuelline and electrics leave the wheeltub, they go between floor and subframe, mainly for protection and distance to exhaustpipe.

As Gilbert said.

The 4 hole design can also be mounted internally or externally.

The advantages of the Icom and zero degree design over 4 holes are that they don't have that big box on the side so you might keep your jack storage etc,.. and the flat valve base on 4 holes can mean you lose a couple of litres capacity compared to a 0deg tank of same dimensions, though not usually in 720x270 tanks.

Not that I'd be concerned but all internal pipes should run inside external venting.

Simon