Can we travel with fresh tank full? We lose half on the way.

I have the same issue on my 2015 Jayco (lots of others do too). Mine has two vent/overflow tubes that stick strait out the bottom. Water "jets" out of these tubes while traveling. Jayco has had issues with this for years. I just put the shutoff valves on mine. Then I labeled the fresh water fill and the water pump switch so I do not forget to open/close the valves.