After yesterday’s flight with the Robin at short and medium fields at 0ft elevation in ISA conditions, it appears to me that the new ground effect reduces the induced drag a bit too much, consequently a bit more/longer cushioning effect than expected.
My recommendation is to increase the induced drag parameters for the current ground effect with 15% and then see where we are.
Also, regarding some comments about the effects of landing aircraft, I suspect that individual parameters for each aircraft should be checked seperately, since it appears that not all aircraft are responding equally relative to the new ground effect. Cessna 150 and Robin feel close to me, but not perfect, in ground effect. Obviously more difference is noticable in the Robin since it is a low wing.