For applicants next year and beyond, this is something you need to ask about at interviews. Most academic programs offer 6ish months standard, some 3, some 12, but 6 seemed to be the majority. The ABR requires residents a minimum of 36 months clinical training (so a max 12 months research) without doing the Holman. Many many academic programs you would not expect, like Cincy, Rush, UNC, Case Western and many of the above mentioned, were very receptive to working with electives to provide up to 12 months, even though its not the norm in their program, if a resident were able to come up with a proposal and get some support for it, be it an ASTRO initiative or some internal award. Make sure to talk to the current residents, because a few places were skeptical that the PD would be as flexable as advertised...not sure what to do with the difference of opinion, but its worth knowing.