One of the comments mentions a do-it-yourself double chainring he uses without a shifter. A response suggests that you nudge with your foot to the smaller ring (dangerous?) and getting off the bike and using your hands to go back to the larger ring. That seems to ruin any ride IMO.
The expected use envelope is the regular gear range is normally adequate, but when you get to the bottom of Hardknott Pass you nudge the chain down onto the smaller chainring. At the top of the pass you place the chain back on the large chainring as you stop to catch your breath, drink some water, take a congratulatory picture and nibble chocolate.