Looking for inovative ideas for auxillary fuel tank???

I have used an electric automotive fuel pump to transfer fuel into a tee in the small vent line of the fill tube. The pump used 5/16 fuel line and required quite a long time to transfer 35 gallons. My main tank was 42 gallons. I would turn the pump on when the main tank gauge was showing about 1/8. When driving, the fuel being used would be replaced so slowly, that I never had an overflow situation. If I had noticed the fuel tank gauge getting close to indicating FULL, I would simply shut off the transfer pump.