rear surround speakers

would it be ok to use 2 center channel speakers as my rear surrounds?
They will work, perhaps not optimally.
FYI - Thiel recommends the SCS4's as both center channel and rear surrounds in HT setup.
Any type of speaker can be used for rears but direct radiating speakers are not so useful if there is limited space at the rear as they should ideally be placed several feet away from the listening position.