My in ceiling speakers are angled. They are Yamaha and, because they are surrounds, they are not where I spent my money. That said, they have handled the surround duty beautifully. My fronts and center are matched speakers. I have always considered these speakers to be much more directionally oriented, which is why I have my speakers on the shelf. You might consider some sort of permeable cloth enclosure (grill cloth panel) to cover them up if you don't find a flush mounted solution.
Previous: 1993 Prostar 205
Red 1998 Ski Nautique, PCM GT40, 310 hp, , Acme 4 blade, Perfect Pass SG/Zbox.
Be kind. Have fun.