Hi Tatter,
So as a less expensive alternative I've been looking into the possibilities that a tension-adjustable European slat foundation might be able to offer me. But... I will be buying a queen size mattress and will be the only one sleeping in the bed. Having two side-by-side sets of slats with a head-to-foot solid bar running down the middle seems to negate the benefits of the slats, since I'll be sleeping in the middle of the bed. Does anyone know if (and where) I might be able to find a Euro-slat foundation where the slats span the whole width of a queen size bed?
In a queen size tension adjustable slat system the middle wouldn't be adjustable and would be the firmest part of the base because it wouldn't flex (or in some cases the side supports themselves will flex but aren't adjustable). The benefits of a tension adjustable base would be less for a thicker mattress or a lighter person where much of the compression forces would be absorbed by the layers above the adjustable slats and it would tend to be more effective on a thinner mattress (say 6" - 8" or so). You would be giving up some of the design flexibility that comes with a thicker mattress that can use thicker layers of softer foam on top but this would be a tradeoff for having additional flex that could be customized in certain areas under the mattress.
I don't know of any slat system that would not have a center beam in the middle in a queen size because without this the span would be too great and the slat system wouldn't be strong enough in the middle and would tend to sag too much with weight. Even a regular non flexing slat foundation needs a center beam to prevent sagging over time in the middle of the foundation.
The Vitaflex bases would also be a "twin" configuration in queen size or larger.
These kind of bases would be suitable in terms of the support they provide for the mattress and are quite popular in Europe with thinner mattresses but since they are an "active" part of your sleeping system (as opposed to solid non flexing slats which are only a solid support system for the mattress) you would need to take how they respond and interact with the mattress into account as part of your choice of a total sleeping system because they would feel and respond differently than a solid non flexing base. There is a different feel to having some extra flex under a mattress vs having thicker and softer layers on top of the mattress and one will allow you to sink "in" more and the other will allow you to sink "down" more.
Phoenix