In 1989 I shot the breakdown of the Berlin Wall (Betacam, ENG of course). The first guy I met from the other side of the wall was a cameraman of the DEFA, the former communist national filmboard. He was shooting with an Arri 35 BL3 and a 25-250 Angenieux Zoom from his shoulder. This is heavy. He told me was doing this all the day. He actually used a wooden stick from the bottom of the camera to a special designed belt.
The 20-100 is 4.5 Kilos, another 0.5 for a LMB2 mattebox and followfocus and 5 Kilos for RED & media, battery. I end up with 10 -11 kilos. Heavy but not too heavy. Especially if you consider the balance options like moving the EVF to the front. For sure not an 10 hour ENG hand held configuration but usable for frequent hand held operation like you have in EFP, commercials or drama.