I have a couple of Paterson Contact Printing Frames (an 8x10 and a 10x12) that have foam on a plastic base and a hinged glass which is closed against the pressure of the foam and clipped into place.

As I am about to begin Carbon Printing I am planning on making a larger (12" x 15") Contact Frame out of a long grain hardwood which will have a 6mm Glass and a three way back (subject to advice from question below) which will be covered on the inside by black felt. The back (thinking of either 6mm Aluminium or Stainless Steel sheet) will be compressed against the tissue, negative and glass by the use of 6x adjustable Hard Rubber levelling feet which will be mounted in 3x 1" x 1/2" Aluminium Bars (across the width) that are hinged at one end and have Spring Loaded Cabinet Latches on the other end of the bars. As the Levelling Feet will be screwed into the bars and locked at the correct height with the use of a wing-nut this gives the option for the pressure of the levelling feet against the back to be adjusted as required.

If I was to use an Aluminium Sheet 6mm x 300mm x 400mm (1/4" x 12" x 16") and the frame was going to be used primarily for Carbon Printing, would I be advised to either have a single full sized sheet, split into 2 hinged sheets in the centre, split into 2 hinged sheets offset (with the split at 130mm) or 3 hinged sheets (with the splits at 130mm and 260mm)? I am planning on making it really well and with good materials so would like to get it right first time, any suggestions will be gratefully received.

TIA, Eddie