Prakash Raj is a much better actor than Sarathbabu, however I feel neither of them fit the role. Btw, isnt Kalki's PS just a very young man (if not a boy!). So Penmai Kalantha menmai would have been appropriate for him then and probably not later on.
Anyway, this movie has all the makings of a low budget fare. I hope they do some justice to the period although personally I dont have much expectations. However, I hope its scripted, acted and directed well.