Limiting Z and Dempster to once every six days is why you don't use a 6 man, but if Harden starts to have a fragile arm it wouldn't be a bad strategy, imo. Couldn't you have Z and Dempster pitch on their normal days and rotate the other 4 guys throught the 3 other spots. Personally, if they did go to a six man rotation, I would want Dempster receiving the maximum rest. Since he's coming from the bullpen, he's going to at least go through a dead arm period, so I'd like to try to keep him as rested as possible.