The VIP seats are available between Zweisimmen and Montreux. As you can see on the map on our Golden Pass page, the route has a lot of curves, so the lightning situation will be different around each corner. Right after departing from Zweisimmen there's a 360° curve, for example. In most places along the route, the light will be best in the morning. The earlier the better, although the sun will be low in the sky very early in the morning and be blocked by the mountains in the more narrow locations of the valley.
Thanks Annika, much appreciated. Regards, Andrew.