Slats are the problem...

I'm convinced that these slatted beds (especially the bowed IKEA slats) are the main culprit for people with issues with a sagging mattress.

The space between the slats still lets some of the mattress squish through. I've tested by having someone lie on the bed and I felt underneath and sure enough, it's pushing through the slats. (3 inches apart).

I decided to try the mattress on the floor and the support is completely different and so much better.

I'm now trying to find a frame with a flat wooden support system or slats that are no more than a half inch to an inch apart. Seriously considering building my own frame with the help of a friend who knows how to build stuff.

Anyone have suggestions for a frame with closer slats or a fully flat support before I go the DIY route? Has anyone used peg board over their slats? I have a thin bunkie board but I feel like it's still not as supportive as when I put it on the floor.