Right, phoned up and spoke to Dan (Ricky's son).
Its not completely clear cut.
The majority of their windscreens go into competition cars. Especially special stage rally cars. Where they need clearing asap. The heater will likely only be on for a short time and the navigator will switch it off after only a minute or so. So full power to both sections.
With it getting 'quite hot' (my words) there is likely to be a temporary 'wavy distortion' (their words) visible through the window. So for a road car and possibly ending up being on for some length of time I would recommend connecting up a two section window in series. You could also fit a delayed off relay.
Full power to an SE5/Coupe half section will draw about 16A so the twin relay & fuse diagram on their web site should be followed I think.
Just unwrapped my Sabre 4 window and it only has one element. I'm going to leave my Coupe in series.
Next time I think about it I could set the rear demist on the BMW and see how long its own off timer runs for.
Hope that helps, but you need to decide for yourself how you want to run it.
Now: '62 Sabre 4, '63 Sabre Six, '65 SE4, '00 BMW E38 740i sport.
Prev: '53 ZephyrZodiac, '64 Sabra GT, '68 Elan S3SE, Mk3 Cortina 2000GXL, Mk4 Cortina 2000 Est, 3 SE6a's, 2 SE5a, SE4a Turbo, 1800Ti.
Company: Cav SRi, Cav SRi 130, Honda Concerto 1.6 (yuk)