How to mount a Letus FE to an HV20

[HBlack]

Question is in the title. Are rails necessary, or is it capable of supporting itself? I was considering building a simple support system of my own rather than spending $100 on a rail system if it's necessary. Also, they give the option of a 72mm or 58mm diameter. As far as I know, the HV20's filter diameter is smaller than this. How do you go about mounting it?

Also, would I be able to get by without a follow focus and monitor, and is going handheld on a shoulder rig possible without a focus puller?

Thanks for the help.