Speaker orientation question

diyAudio Member
Joined 2007
Just bought a new cheap H/T amplifier.
Not Dolby Atmos, just an old HK 1710S. If using the 2 channels from the 7 available for Front Height and using some spare centre channel speakers is it better to use then vertically oriented or horizontally?
The speakers are nothing special, just Sansui WTW using 5" drivers, I have however blocked the rear firing posts and stuffed with fibre as they sound cleaner that way