Call Todd @ Towee, he'll be able to tell you if anyone is guiding out of one of his boats...
As far as fishing in the Keys and Florida Bay, it HAS been done, there's plenty of photo evidence of Towees down there. There used to be a video running around of some guys crossing the Bay in three foot seas...I guess it depends on your boat skillz and your pucker factor....
As far as monster tarpon, I have yet to see any pics of guys grabbing face on big fish out of a Towee...but again, Todd may be able to provide evidence. He's a great guy, keeps in touch well with the owners, and is familiar with the Keys...