Table Mirrors

I am doing DIY CP's I want to sit my floating candles/vases on mirrors....what size mirrors should I get? at least 10' right?

I believe the cylinder vases I want are 3' in diameter so If I want to sit 2-3 on the mirrors, it makes sense that they be at least 10'

does this make sense LOL?

Also do I have to use round mirrors or will round vases on say an octogon mirror look ok ?

TIA!