How big of a tank do I need?

[gobytron]

There have been studies done, and referenced on this site as well as reef central that this is something of a myth and that these fish will be just as stressed out in your 6 footer as in anything viable for the average hobbyist.

I'm contrarian.
i think that 55 will be more than fine, especially for just 2 months.

If it were me, Id be more worried about aggression between the two than anything and might just keep them in seperate, smaller tanks (maybe 20-30 gallons like you'd find these fish in at ANY LFS) until your big tank is ready.