Our dojo has for four years had a relationship with Kenji Kumagai 7th dan, who was a student of Hirokazu Kobayashi, 8th dan, an Osaka based deshi of the founder. Because of Kumagai's influence, some of our waza are decidedly non Hombu (or should that be non Kisshomaru?), particularly irimi nage, as Goldsbury sensei has mentioned. Its apparently closer to the irimi nage of Tomiki or other prewar deshi of the founder. Our dojocho once trained with a deshi of Nariyama of Shodokan, Mike McCavish, who said that the irimi nage styles were very similar.
It may be a bit more direct then that. Nariyama Shihan was of course a student of Tomiki but was also uchideshi in the true sense of Hirokazu Kobayashi (actually lived at his home) over the course of six years.
Shodokan Honbu has always been an Aikikai dojo with Kobayashi H. regularily teaching there (his own classes and also to the Shodokan people) and since his death his student Kimura continues to teach classes at Shodokan Honbu.
The body type of Nariyama, Kimura and Kobayashi are all very similar and quite different from Tomiki and there is a pretty good consensus that much of what defines Nariyama Shihan reflects this. Kobayashi died a few months after I joined the dojo but when I compare Kimura and Nariyama I agree completely.