Input EMI filter design for two parallel DC-DC converters

[Phil Smith]

Hello everybody,

I'm in the process of design a power supply for my simpit display. Basically, it is a 24inch Samsung monitor and raspberry pi driving it.
Main power supply is +27VDC (nominal) which coming from external AC-DC converter via 5-7m cable. Grounding is done via simulator's metal chassis, therefore there is no negative wire.
An EMI filter is being designed using this series of videos: https://www.youtube.com/playlist?list=PLE3Pq-hBtiMS-1gFecr9FcBjf_p4joRZP
Please find attached the block diagram of the supply.

I got couple of questions please regarding the design of device's input bulk capacitor size and EMI filter.
1) How to calculate C_bulk in this configuration?
2) Is it correct to assume, that total input impedance of the power supply Z_in for EMI Filter will be sum of parallel input impedances of each DC-DC converter Z_in = (Z1_in * Z2_in)/(Z1_in + Z2_in)?
3) In my case input ground is chassis, so is it correct to connect common mode caps 0.5*C_cm from each line to ground node before common mode choke as shown on my diagram?

Any help is much appreciated.

Kind regards, Phil.