Be careful... I don't know about Hondas, but on other cars you can "overfill" a tank. Since 1996, all manufacturers have been required to comply with OBDII (second generation emissions monitoring system). That monitors vapor pressure in the tank to control hydrocarbon emissions from unburned fuel (evaporative emissions). Overfilling could mess with vapor sensing equipment on some vehicles. Then, there's the vapor recovery system on most cars... fuel vapors are recovered and burned after being collected in a charcoal canister. If you fill every space in the tank with fuel, you could force liquid fuel through the vapor recovery lines and the canister, possibly damaging it.

Again, I don't know about Hondas. Can anyone comment on this possibility on the HCH?