I have 100L combined in my 2 sill tanks. Being a 90 I have nowhere else to put extra fuel storage.
I have a pump at each tank, and pump it through a tee piece that joins the two lines into one, and then it flows through to a tee piece on the filler line to the main tank.

This lets me pump straight into the main tank. Just like at the bowser.

To stop over filling problems, due to the fuel gauge being very slow to respond while the engine is running, you can use an Ultragauge etc to see what percentage your tank is actually at.

In my case, I have a single point filler system. This requires a forked filler piece (from Mulgro) so you can fill either tank from the same filler. It also means that if you leave your pump on too long, then the main tank overflows back into the other tank. No harm done. Plus I didn't have to cut holes in my panels for the new fillers. The breathers from my sill tanks are also linked into the breather from the main tank making it a sealed system.

Mulgro can also supply OEM style switches with fuel bowsers on them for identification. Back lit and everything. Observant passengers think mine are pretty good. :-)


Phill.