i still feel half step plus granny is the way to go. i started this type of system long before indexed rear derailleurs were developed & i certainly know how to double shift. it is easier to double shift today with indexed deraillleurs & handlebar end derailleur controls i have 2 21-speeds with 12-14-17-20-23-26-30 freewheel clusters (not cassettes) on both bikes. the road racing frame has a 24-44-48 chainrings, the criterium frame has 26-44-48 chainrings. the two different bottom bracket heights affected how wide a difference the 1968 or so model campagnolo record front derailleur would handle. i have one truly wide range crosssover that is a 54-speed with a schlumph mountain drive because i can no longer ride a diamond frame. that is on a greenspeed gto, half step plus granny will not work with 20" dia. wheels. you may also like to see what john allen says about half step deserving a second look under gear theory in Sheldon Browns Bicycle Glossary site.