IMHO:
With only aeration (that's WITH the water conditioners that I listed, plus the salt in the water), I'm not comfortable transporting more than 1/2 pound of trout per gallon of water. With O2, chemicals AND aeration/agitation I've hauled 1# per gallon.
Other people with more fish hauling experience than I have should chime in if I'm pushing the limits. I'm a newbie to hauling fish compared to others here on the forum.