I went with a tank extension and few issues I've found are.
Angle of tank can reduce effective size.
Take off on the side again reduces effective size.
You need your return to return to the swirl pot if you dont you can empty it quicker than it will refill when low on fuel.
Its better to have walls/baffles around the pot, if your take off is to one side you need to hold as much fuel as you can in the pot. Centrifugal forces when cornering will move the fuel especially when near empty.
Definately fit a pump pre filter, sytec do one for around 20 quid that can have different fittings to match the pump.
I think a good size would be around 1litre with baffles above.
My efi system is Sierra so reg and pump is ford, i have the pump mounted behind the diff level with the take off.
Jez