Word has it that the 66's need to be up off the floor and well isolated for the bass to perform properly.
I am fitting 3 of these "Soundcare" feet to each speaker base. They are like a spike which caries round its own floor cup/shoe, the big stainless washer is to prevent the fairly small diameter neck from biting into the veneer.
These will then stand on a custom made concrete plinth with a profile that matches the cabinet. This will have 4 adjustable spiked feet and a spirit bubble set into the centre, allowing the plinth to be levelled before putting the speakers in place.