Hi Karen,

Thank you for your question.   The MDF does not need to be too thick, approx 3mm to 5mm will be sufficient to support your mattress.

As far as coverage is concerned, we would recommend you cover the whole area including the central spine.

I hope this information is of assistance, but should you require any further help, please do not hesitate to contact our office on 0161 437 4419.

Kind regards Julie