Dirk was certainly more of a stretch for RD, particularly after his "transformation," in which he chewed everything, including the scenery. I enjoyed some of his scenes as Jeff Clark, but there was too much soap opera-type love scenes w/ Vicki, which didn't seem to work too well chemistry-wise. Least favorite appearance has to be Ned Stuart, though to be fair, he had a few good eps there, too.
Petofi