I don't really see why you would need any appreciable time in a cessna to prepare you for a regional. Flying a single piston is not indicative of the flying you will do at an airline.

Between the CTP and initial you'd probably end up at around 30 hours of time plus another 30 on IOE. 60 hours in the actual acft(or a close equivalent).

Maybe get an hour or 2 and do an IPC, anything further is a waste of money at best.