So Gree is 2:48, Tion Medon 1:96 & 4-arm Grievous is 1:96.
Yep - final confirmed ratios:
28:96 - Clone Trooper (Ep3)
24:96 - Darth Vader (Ep3)
15:96 - General Grievous (2-arm, with cape)
8:96 - Sidious/Palpatine (Ep3)
8:96 - Anakin Skywalker (Ep3)
7:96 - Tarfful
4:96 - Commander Gree [Clone Trooper Box]
1:96 - Tion Medden [Tarfful Box]
1:96 - General Grievous (4-arm, no cape) [Grievous Box]