[Petr Brezina]

Thanks Chris, thats very useful discussion.
You can be right about the sketch, true is that we still dont have any drawing with the carrier and WS mounted in the UC.
Regarding the folding seat - there is a welded plate coming from the engine cover which supports seat in down position, you can even bolt seat to it (mine is missing hole in it, but should be there - now I believe to know why is this that hole there for - no such hole on the gunners side). So I believe that it could be very rigid and sturdy support.
Im obviously missing something WS carrier is locked in on the outer edge of the seat.