You can use a short target placed not so that it can't be had, but that the shooter will maybe forget to reset their turret and be a turn out for the next one.
Even when there is "no wind" there may be a little bit of drift, and I often make the first target in the lane the longer one, so you don't get the chance to see any slight movement with the shorter one as a guide.
If you are allowed, a change of faceplate colour is useful.
Sometimes we'll have a target say 50 yards set low down to the ground and in a lane that has been cut two mower widths in long grass. Can look quite different from open ground.
Helps also if you can make the targets in the previous lane not easily visible. For example, shooter ranges and hits one target; if the next lane has one visibly at the same distance they'll know the settings as they got the last one right. Make it harder to compare.
Not wishing to open a separate dialogue, but down here we have non-BFTA local rules and we can place 25mm kills out past 35 yards, and have 25mm positionals to 20 yards. A 19 yard inch kill stander compared to a 30 yard full size, some will see one as harder than the other. Just a confidence knocker.