The VP center speaker tweeter is designed to have a horizontal dispersion when orientated correctly. Turning them on end defeats the whole design, so you would be better off purchasing a speaker designed to be vertical.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85