Toby,
Along the same lines as Guy's response re:overall sword size, Hayashizaki was believed to have used a very long sword overall. So, the tsuka would also have been quite long. As I understand it, most branches of MJER today use much shorter weapons (except perhaps Komei Sekiguchi Sensei's branch). In contrast, many MSR teachers encourage the use of the longest sword that a practitioner can properly do nukitsuke and noto with (but probably not nearly as long as Hayashizaki's). The big monsters used by Shin Muso Hayashizaki Ryu and Sekiguchi Sensei's MJER are probably closest to what Hayashizaki used, and probably still adhere (more or less) to Guy's proportion rule.
Regards,
Brian Dunham
MSR SanShinKai