Question about Karup Design Ziggy

I was able to fit my two slatted frames, each 70 cm, well into the bed frame. I think that works for any size.

I would say yes, because you can sink the mattress relatively deep. The bed has a "static" slatted frame (boards from left to right), but you could easily place another slatted frame on top of it. But I am not 100% sure.