Sir_richard and I have been analysing scout endgames on gravon. The scout is able to be captured with 4 pieces, in nearly all "normal" gameplay positions. This is the most complex position we found where it was possible to capture the scout with 4 pieces:
This is a difficult position and certainly not easy to force the win here. On each side of the board there is a 6x4 box, which we wager is the minimum squares necessary to capture the scout with perfect play from the scout. Any more room, and the scout will be able to escape.
The scout's goal is to fly between the top and bottom, and the pieces first have to force the scout into one of the two 6x4 boxes before progressing any further.
As an illustration, a position with no bombs first 3 rows requires a minimum of 5 pieces to capture the scout, as the scout can otherwise alternate between 3 available squares. It is impossible to capture the scout in the below position.