I am on the staff of an ATC Gliding School (winch-launched) in Kirknewton and have to say that the Dayglo panels assist to some extent in seeing a glider that is within (say) 700m, dependant upon aspect angle. If the glider is over that sort of distance, I can often see the glider outline, but cannot detect the Dayglo panels. The panels appear to be more visible when the sky is overcast and grey, rather than light and sunny with scattered fluffy Cu clouds!