Search words/web sites: stuttering, stammering, speech pathology, speech therapy, "which syllables are most likely affected by stuttering?" I looked at The Stuttering Foundation, National Institute on Deafness and Other Communication Disorders, Information about Stuttering, and an abstract regarding distribution of phonated syllables in people who stutter. I ran the terms through Google, Yahoo, and several medical search engines.
None of these contained the information I need to know: which letters and sound combinations would most likely be affected? Would he repeat full words, just their beginnings, or would he also stumble over endings?
I want to make his speech realistic without causing readers to trip over it and ending everything he says with "he stuttered/stammered" gets old.