Dunlopillo and slatted bases

My wife and I had a Dunlopillo Diamond king size mattress for over 15 years, which was on a pine base with slats further apart than recommended by Dunlopillo, but that did not seem to cause any problem.

We replaced the mattress a few months ago with another Dunlopillo Diamond but find that the specification has changed.

The mattress is not as comfortable as the old one was (before it started to sag too much, which is why we replaced it) and there is a perception that it slopes towards the edge of the bed.

The middle of the bed feels firmer and more comfortable.

I am wondering whether there this is simply a characteristic of the mattress, or whether we could improve the comfort by one of the following: (1) adding more slats so that the gaps are reduced to the size recommended by Dunlopillo (2) completely replacing the base with a sprung beech slatted base.

I have seen that some of these have special slats in the lumbar region where the tension can be adjusted.

In a king size bed there would be two sets of slats that could be adjusted separately to suit both sleeping partners.

I would appreciate any advice you can offer.

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