If there is nothing laid down I would try as a starter looking at the relationship between stall and best glide speed, i.e. if stall clean is 60 and best glide clean 1/3rd more at 80, for a flap down stall speed of 48 you would be looking at at glide of 64. This might not be totally correct and might be worth trying it at differing speeds to find the proper speed, but at least this gives a figure to start with.
Having said that, where you will end up is probably going to be more affected by the wind and as said by others in this thread, get the nose down, look where the aircraft is going and do your best to put it in the best area available.