They look cool. I think they would look even cooler if they were a complete bag and not just an extention. I know... I am talking about alot more money, but think about all the extra space you would get.
Check the classifieds. I've got the whole shebang for sale.
FWIW,I checked out some new extended hard bags available from Ness and wasn't very impressed. They looked like they were made with the chopper gun process and not the hand-laid method.
I wish H-D would make their hard bags deeper and wider than they currently are. Most half helmets will not fit in the stock H-D bags.