Where to get 60 and more inch Ribbons???

[Studley]

You reduce excursion by limiting low frequencies...not top.
Introducing crossover and source of high frequencies not coinciding with midrange is.

Well there would be a crossover in any event. As you will know, every design choice represents a choice between compromises. Potential dispersion pattern mismatches has occurred to me, but trying it is probably the only way to find out how audible the potential mismatch is.