Power combiner 200MHz, coaxial type

Hi all,
I have to design a power combiner narrow band (f0=200MHz ; Δf=10MHz ) capable of about 6kW output and 6 input ports.
The idea is to have a central coaxial feeder a radial transmission line and n (6 in this case) N type 50Ω connectors.

I have got some problems in simulating the radial transmission line. Should the substrate be attached to the outer conductor of the coaxial feeder or to the inner? How to match the N connectors to the radial transmission line?

And again any hint how to simulate it with HFSS?

Thanks in advance for your help!