Re: Suggestions extra gas on long trips
At an average of 10 mph (real time, which includes stops and slowdowns) you aren't going to get much further than 50 miles away from home unless you just get on the bikes and run them hard for a whole tank.
You have about 50-100 miles of range. More if you coast when you can and run the bike easy.
So, you only need to carry a gallon between you both, should be easy for each of you to carry a half gallon of liquid.
Test plastic first by leaving the container filled overnight, and watch static with plastic containers too.
If you are just going "out" you'd be surprised at how far you can get (and back) on the stock tank.
You can also replace said tank with the larger available options.