Doing the LHD version throws up all sorts of questions. I am unable to use the existing flutes into the demist plenum. I am concerned that any amendments may not come up to scratch. I am interested to know the opinions of other builders concerning the efficiency of the demist system. I realise that the absence of a cabin exhaust outlet can affect the efficiency of the input. However, If I change the input flutes to a position at right angles to the output, to get an even output I will need the plenum to be under pressure. At the moment the output ports exceed the surface area of the input ducting and therefore there is no general increase in pressure in the plenum resulting in air passing straight through the ports nearest to the input. Opinions please.