Mast compression support across cabin roof

[sailingpeter3]

I've recently come across two Mk 111 Top Hats that don't have the "signature" Top Hat steel mast support across the outside cabin roof. Looking inside the boats there is the usual two wooden mast support posts, but its hard to tell what's directly under the mast (a beam going across the two support posts?). Does anyone know how the masts on these boats are supported? Anyone heard of any problems?

Cheers,
Peter