No, this isn't about wierd meeting venues for ac/dc couples, so cool down.
Walked away from a big job yesterday because they were insisting on having duplex bars to create 6-pane casements. Granted, they would have looked fine aesthetically, but if you stick them so that they don't come off (and there are various schools of thought on the relative merits of silicone and double-sided tape, I prefer the tape), if the unit fails - and some manufacturers now are only guaranteeing them for five years - then the bars get destroyed in their removal and you then have to make a complete new set to match. You've also got the hassle of having to provide a template or temporarily board up and use the old unit for the manufacturer to correctly align the separator bars to match the existing.
And that last point is problematic because even the best unit manufacturers can get the positioning wrong by a couple of mil and that looks bloody awful because you can't hide the discrepancy, the manufacturer insisting on their right to claim that as a manufacturing tolerance!
All that and you only get a replacement unit, no one's paying for your time because the warranty is down to you.
I've only ever used duplex bars once, on a door. It looked great but I swore then that I'd never do it again.
At yesterday's meeting I showed them drawings of alternative fenestrations, still totally 'in character' with the Edwardian building, using standard bars, but they were insistent on duplex despite all the potential problems - and they'd recently been told by a neighbour that theirs had fallen off when they cleaned the windows. There was a certain irony there because when I first surveyed the job earlier in the year and they said they wanted duplex like the neighbour's, I'd said then that they had a tendency to come off but the neighbour had said, then, that he'd had no problems.
So? What's your experience?