Problematic plume from condenser boiler

When my Vaillant condenser boiler was installed 2-3 years ago, the flue was installed so that the emitted plume of water vapour hit the soffit boards and guttering of my detached garage opposite. Not ideal at all, but we (the installer and I) did discuss all the possible options for where it should go (including all the extensions and adaptors available), and to cut a very long story short, this was the best compromise and I'm stuck with it.
At the time I fixed a sheet of h/d blue polythene over the affected area of the garage to prevent damage from the perpetual steam bath (it's not hot, just warm and damp), but SWMBO would prefer a rather more attractive solution, and 2-3 years on, I'm finally getting round to it. I therefore propose to knock up a small sheet metal deflector for the plume, so that essentially a small sheet of aluminiunium is mounted about 1.5 inches in front of the flue output, at about 45 deg, so that instead of coming out horizontally, the plume will be deflected upwards a bit, tipping it above the garage gutter and over the roof tiles. The bottom of the deflector would be well away from the wall/flue, so that any condensate will just drip off the bottom would fall to the ground.
Mindful of the fact that the Vaillant engineer roundly condemned the positioning of the flue (in writing) when he recently came to service the boiler! and that this would be a "non-standard" solution, can anybody see any flaw in my idea, before I start?
(Second query, where the heck would I go to buy a small sheet of aluminium [1/16"] about 20" by 12"?)
Thanks David
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Don't know exactly what the Vaillant flue is like, but would it be possible to fit a TEE over the external pipe to allow the plume to separate and dissipate over a wider area ?
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It's about the size and shape of a can of beans; the majority of the plume issuing from the end, and has drain holes on the underside.
Thanks for the thought... It would work, but I thought a deflector would probably be more 'politically' acceptable since it doesn't involve modifying or physically attaching anything to any Vaillant kit. Also, with a tee-piece, steam could rise and affect the soffits of the house (the house roof is very low).
Cheers David
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The larger B&Q stores sell small sheets of ally. More expensive than an offcut from a fabricators, though.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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