I'd be more concerned about running the tubes underinflated at speed, causing a rear seam failure.
>3.0 psi is mandatory. You need to check the boat after it's been in the water about 15 min, and the cold water has had time to cool the air, reducing the pressure.
Also, if there's an extreme temp change (IE, nightfall), you probably need to top off before the return trip home.
Buy a 12v electric pump.
Gluing geek since 2007
Opinions and intepretations expressed are solely my own and do not express the views or opinions of my employer