I can sympathize with Poncho's point of view. My 283 is very fuel thrifty for all the punch it gives, but I would be filling up every three days. My Rat is used as a daily driver. Plus in California, long distances to car shows is the norm. Try driving 600 plus miles round trip to a meet and fill ups become a pain in the butt.
Safety should not be an issue with a fuel selector switch. You'd never want to drain the tank dry anyway. Look at the trip meter and when 200 miles rolls around switch to the tank that has the gauge. Sure, you never use all of the 21 gallons but I wouldn't want to do that in any case. Not much to it.
Shortstep's comment is an interesting one. However, I think it will be easier to have the one tank lower than the other from an installation point of view. Using a fuel tank selector switch, although not my first choice, seems to be the way to go to avoid all the issues of fuel levels, heights, etc.