My brother in the US had a 2.5 car garage with a single wooden faced door
made in a similar way to how you describe. This worked but had been
retro-fitted with what resembled the strutwork from a biplane on the
inside.... and it still sagged in the middle when raised. The opener was a
very hefty winch, the sort that made the lights go dim when operating.
Real timber will be v.heavy, thin timber facing on a conventional steel door
may be an idea?

As MMcN sugests, side openers may be the way to go for a wide opening.
Henderson do tracks & hangers for either Z-fold doors or alternatively
tracks that can be formed into an 'L'.
Not too expensive at all, and 33" FLB doors are only £45 each which is not
bad compared to making them.
33" x 6 =198" __/\/\/ \__ or __/\/ \/\__

--
Toby.

'One day son, all this will be finished'