Hi aurorajp,
Like you I have some reservations about the wire grid foundations with all latex mattresses (see post #10 here). In the case of My Green Mattress though … it is a higher quality Powerstack foundation and they have upholstered it with organic cotton so the “gaps” would be filled in and better supported.
I should also mention that there is no consensus at all about wire grid foundations among manufacturers and there is no “proof” that one opinion is more accurate than another. For me … making sure that it has a good cover or upholstery and is more evenly supportive is just a matter of caution because of the highly elastic nature of latex. I should also mention that they offer a slatted foundation that is all wood for those that are concerned with electromagnetic fields which is another issue (among many others) where there is little consensus and many different opinions.
Phoenix