Fred,
Just been down to Mymo P27 No.147 and taken the following measurements:-
Max height under companionway hatch 71" or 180cm
Max height immediately forward of the companionway hatch 68.5" or 174cm
Max height at forward end of saloon against heads bulkhead 67.75" or 172cm
Max height under saloon forward hatch 70.75" or 179cm
Hope this answers your question
P.S. My saloon sole has a 10mm thick holly strip effect ply board laid directly onto the glass surface.