The mast step was sealed in polyester and glass matting, and while looked OK it had a hollow sound when tapped. I opted to replace  the mast step too. As the forward bulkhead was bonded to the mast step this too needed to come out. The mast step was as it materialised heavily decayed. It looked to be made of Douglas or similar. The picture below shows it replaced with iroko.

Mast Step and frames

Note the bulkhead is removed. I have stiffened the hul with a glue lam frame made up of 5mm strips of Douglas. The deck beam of iroko can be seen.