He's looking at a 5.0 mast, which should be identical to a H16 mast with the G-Cat mast-step base. My G-Cat 5.7M mast is a H16 extrusion that is (obviously) longer and has spreaders added.

I believe the mast and rear crossbeams are the same extrusion, while the forward crossbeam is a H14 mast section. There are no complicated systems on the boat, and if the rudders fail you and you cannot repair the (absolutely wonderfully designed) system a H16 or TheMightyHobie18 system can be retrofitted. Vector Marine will be producing a G-Cat F16 in the near future, though I doubt it will have much in common with it's predecessors beyond hull design.