I've only ever had small orchids mounted (@ least compared to what u r talking about! Lol). I know most ppl just take the mount the plant is on, that has been outgrown, and just attach to (on top of, to the side of) another, larger mount. If you need to divide a plant that's on say, like a flat piece of cork/tree fern, you could just saw the whole thing in half to divide, if need be.
Talking about mounting them to large pieces to begin with... As long as you have space, I'd say go for it!! (*oh my gosh, you have to post pics! Lol, I have to see that!
) That would be really cool looking with some of those large driftwood pieces! I've seen the ones you are (or I think you are) referring to, and that would seriously be really cool looking! Ooooh, u are in Florida
... You could do yard art with these, & have large driftwood all throughout the yard, with orchids attached... Damn... I'm kinda jealous of where u live right now! Lol (although, tomorrow afternoon, I might feel differently... Assuming y'all r hotter than we are here!
Lol)
Good Luck! I can't wait to see what you end up doing!