LyonhaertMobanditothanks you. it looks like my Clipper only gets around 100ly on a tank of fuel
Fuel tank size is actually not the same. Both have class 5 FSDs, so if the FSDs are the same then they'll have the same max fuel per jump. But the Clipper's default fuel tank (4C - 16 tons) holds half the fuel of the Python's default fuel tank (5C - 32 tons)
You, Sir, are correct. I looked right at it last night and didn't see it, but the Clipper packs half the fuel, and has a (default) hull mass of 400t, to the Python's 350t. Then factor in loadout, etc for total mass.
Mobandito, you CAN equip additional fuel tanks into your optional internals for greater range if need be.