Hi, we have a king size Tempur mattress which we used to use on an old divan base, which was comfy but I never liked the look of. We just moved house and bought a sprung slatted wooden bed, which looks great but we quickly found the mattress and base were incompatible (felt like we were falling through it!). Read on you site the MDF idea which we have done, and works quite well, though it now feels a little firm. I went for 18mm thickness (didn't see your other posts advising 3-6mm!) which feels much more secure though I am a bit concerned about the extra weight on the frame, of the MDF and my partner and I (combined weight of about 28 stone).
I believe I should put some holes in the MDF to aid air flow but not sure how many holes would be needed or how big they should be. Any advice would be gratefully received.