I've never heard of "brush flies" but I tie a lot of big streamers here for the northeast salt.
Big flies on big hooks that carry a lot of bulk actually need to be weighted (as in a keel of lead strips) to get them to cast well and ride up-right.
Casting those are not fun to me.
And if you're not having fun, then why are you out there in the first place?
If you're not carrying a lot of bulk.... and you should do everything possible to avoid that...the only reason to use oversized hooks is for the added hook strength.
I don't know what kind of fish you're targeting, but a 6/0 is likely way over kill.
Where I fish, an 8inch fly is all you will ever need . Even if the baits are larger. And nearly any 8inch fly will ride easily on a 2/0 hook or even a 1/0.
(I do tie a 3/0 bendback but that's only because it needs the additional weight to ride upright)
:icon_idea Keeping your bulk and hook weight down is paramount to having a fly that you actually might want to cast more than once or twice a day.
Here in the northeast salt, flies are tied to give the illiusion of great size.
Even the Clouser Minnow was originally designed to appear as if only the shoulders and back of the "bait" was visible and the region under the lateral line was just implied.
Bob Popovic's "hollow fleye" series are just that..hollow.
They're reverse tied (like a thunder creek) so that the material is forced out from the hook shank.
"Flat wing" style flies, like that one pictured in post 3 are the norm here in southern NewEngland.
The "Rhody flatwing" is my go-to fly for most of the season. And I never tie then on larger than a 1/0.
There's no point to it. You're keeping your material bulk to a minimum and a 1/0 is a plenty strong hook with a lot of gape.
hollowfleyes
Flatwings
hollow flatwings !