So, at the beginning of this endeavour, I noted that a good tank shows 250 miles at the midpoint. My first full tank of this experiment was encouraging and was something like 262 miles at this point, but here we are in the middle of the second tank and it's merely what I expect to get at the middle of a good tank.
And here I am. Am I discouraged? Not in the least, as every tank of gas is different. This tank spent 4 days at home, running periodic short trips in town, which is not the best way to improve mileage.
So I declare the jury is still out, and will wait for five full duct-taped tanks before arriving at a tentative conclusion as to whether or not this is a smart or dumb thing to do.