Given the innaccuracies in standard Cessna fuel gauges you could do worse than buy a dipstick.
It'll at least let you know how much juice is really in the tanks after you've make your first landing. This will avoid the awful buttock clenching, sweat inducing moment when the gauges lurch toward empty even though you "know" there's another 1.5 hours worth in the tanks......
I'd agree with
bose-x and plan on 6gph not 5. It always worked on my old Aerobat after I'd had the moment described above. (I DID have well over an hour's fuel left by the way
).