Lay some knowledge on me, fine people of BF. My wife's bike is a tiagra triple 9-speed and I obtained a 11-32 cassette to put on her wheel instead of the 11-26 that came on it due to excessive complaining about how hard hills are. (she's had hip replacement surgery and getting in and out of hour street requires a few pitches of about 18%, so it's really not just whining)

Anyway, I cannot get the RD off the cassette. The b-screw doesn't appear to have any positive effect. One theory I developed on Sunday is that perhaps the chain is too long - I can put the bike in the large chainring, large cog and the RD still has plenty of take up. If I push down a bit on the chain between the crank and the cassette, the RD moves off the cassette quite nicely, leading me to think maybe losing a pair of links would work. It's highly probable this drive train isn't meant to accommodate a 32 tooth cog, so if there's a possible way to engineer a solution, I'm interested. She spends more time in the low gears than the high as it is.