Hi ydelle,
No … I would avoid the ones that are missing the wires in the middle section and I would also be cautious with the ones that have fewer wires (such as 6 or 7 longitudinal wires) depending on the type of base foam was in your mattress and on the importance of saving a small amount in terms of price.
The first post of this thread has my thoughts about the “grid type” foundations in general and my preference for the ones that have more wires and a smaller grid pattern. Overall though the more longitudinal wires there are and the smaller the gaps the more evenly supportive the foundation would be and the less chance that the foam will sink through the gaps over time.
If you have a mattress with a latex base then this would be even more important because of the elasticity of latex. With a polyfoam base layer it would be less of a concern but this would also depend on the elasticity and firmness of the polyfoam. You can read more about this in post #10 here.
Even with a polyfoam base though … I would tend towards a version with more wires and a smaller grid pattern because it is more evenly supportive unless the small difference in price that goes along with higher long term risk was worth it to you. I would also make sure that whatever version you choose meets the criteria of the manufacturers warranty.
Phoenix