Speaker plinth material bottom ported Zu Omen Defs

Currently my Zu Omen Defs sit on hardwood floor ( bamboo) in my basement finished listening room. Even though we are very good at keeping sewer cleared, video checks every year, I’m always paranoid about water overflow. Our basement is bone dry. I would like to raise the zus off the floor about an inch or two with a plinth. IMO, mapleshade’s at $600 + each is pricey. I can make my own. My question is wood vs granite on bottom slot ported speakers like Zu. One would think that granite may be too reflective for bass vs wood. Just curious if anyone has any thoughts. For the trolls: yes we have flood insurance, sump pumps, etc. I’m not moving the gear back upstairs. Just asking about best material. 

Thanks