The Hubble was designed to fit into the STS bay. Like the STS, the Hubble is getting pretty old. My view, FWIW, is that the Shuttle should be retired immediately and the completion of the ISS abandoned. If the ISS is to be completed, it should be done with expendible heavy-lift boosters. Also, the pieces of crap ISS modules designed and built by the Russians should be removed and jettisoned.
If the STS is to be flown at all, it should be for repairs to the Hubble. However, a repair bay for the Hubble could be launched with the same expendible boosters; the Hubble could be taken inside (robotically by remote control from the ground); the technicians to do the repair/refit to the Hubble could do so in a shirtsleeve environment, and arrive at the bay using the new crew vehicle now being developed.