People generally seem to fit several blinds across big windows - eg the Ikea Hoppvals ones only go up to I think 150cm, and you just fit multiple drops. But now you mention it I don't know how that would work with the 'perfect fit' ones.
Hoppvals isn't foiled, and I'm wondering how much a difference that would make. Suppose I should buy a giant roll of sticky paper and a roll of foil and try it...
Theo