According to GFA MOSP2, Section 18.8.2, when a tug is at full stretch of the 55m tow rope for an aerotow launch, the tug must be 60m downwind from the displaced threshold [piano keys] on all runways. This means that at launch, both the glider and, by definition, the forward-most operations vehicle, must be some 100m from the piano keys.
To help us comply as best we can with GFA requirements for launching gliders, we already use two markers to assist all of us parking operations vehicles. On R19, there is the bright yellow marker fixed to the dirt road. On R27, the fence corner is the position indicator; any further east and we would be blocking our access to the field.
At the launch point of each of the two other runways (R01 and R09), there is now a fence picket painted bright yellow to help us position the forward-most operations vehicle.