Compact Crank AND MTB cassette?
My first post here, although I've been lurking around and soaking up some good info for quite a while.
I recently got back on the bike after returning from Iraq, and my girlfriend has just started riding this past summer. We have both signed up for a very hilly century ride, climbing Alabama's highest point twice, which literally runs through her backyard. She has pretty good endurance, but steep climbs where a lot of power is required is pretty much murder on her. Right now she's running Ultegra 9 speed, with 12-27 in the back, and a 53-39 up front. I have a 9 speed compact crank on the way, which should be here sometime this week, with a 50-34. So my question is this: Obviously running the compact crank will give her lower gearing, but since she is running 9 speed, has anyone had experience or opinions about running a 9 speed MTB cassette, such as a 32 or 34 rear? I read that an Ultegra triple rear derailleur would be necessary, as well as adjusting the chain length, but has anyone done this? She would probably stick with the compact crank once we get it, but the MTB cassette and derailleur would be used for just this one event, since there is so much climbing, and I would want her to have a decent shot at finishing, and also have the best experience possible, without hating each and every steep hill.
I thank you in advance it guys (and gals) and any input would greatly appreciated!