Peter,

Stretch???....you referring to rope stretch, that depends on brand of rope used but we are getting nil from the stuff we use. It has enough purchase that my youngest's crew can haul it down to the black band with not too much problem.

Water getting into the mast...well if you have got it into a position where it can enter, I think you would have other problems too, it is only open at the very base where the exit blocks are.
Yes the mast sits on the bottom assembly, so the step and plate are one unit.
Yes again, that it the mast rotation spanner, located anywhere else it fouls the blocks and lines that are internal, and we like it low and running back off of the centre beam, not off of the boom like some other set ups.
I will get some other pics and email them directly to you unless there are others interested.....might do both.

Food for thought and another option.

David