I had a demo of a 6m Avatar with a 230hp Claas and it used all those horses on slopes. The demo machine had 1.4t of weights on it for penetrating into hard ground which I wouldn't need so that would improve it a lot IMO. The unballasted version was still around 8 tonnes empty. On gentle slopes I think your 6215R would be ok as long as you don't want to put beans in 3" deep at 16 kph.