Do you reckon, as a basis Conor/Big Neil's formula is a good starting point :
20% reducers (35yrds and under)
Extend the distances of positionals, vary the course shooting line so it twists and turns to make use of any slight wisp of wind there might be.
Throw in some angled shots but don't over do them (3 or 4 lanes as a guide)
Include some shots on uneven ground, but again don't overdo them (3 or 4 lanes as a guide)
Throw in some difficult ranging conditions - dark targets, targets with different faceplate colours
Vary the distance of targets in the same lane, try to avoid having both targets at roughly the same distance
Vary the horizontal angle of targets in a lane - don't just have two targets facing you
Include some lanes where you might need to move your beanbag between targets, but not many of these
Add some fun targets with different faceplate designs
Anything else to add to the formula?