Sounds like you are now going the custom route with your top, but here is some additional info about my GTRV top. There are more details and photos in my build thread
I have a T-top; Coast Outfitter/GTRV also makes a V-top, which is hinged at the rear of the van like a Vanagon or Eurovan Westfalia top. The top is fibreglass with a plywood core and wood ribs. It is very solid - I can stand on it (closed) with absolutely no flex. Fantastic Fans can be installed anywhere in the roof.
Photos of the top closed.
As I mentioned in my build thread, there is a fairing that extends over the cab in front of the roof, making the top quite aerodynamic (heh, it is a full-size van, though!). In fact, the top is very much like a pre-hung door, with both the top itself and a frame (including the fairing) installed on the van. In the "open" photo above, everything you can see above the gutter and blow the fabric, is the one-piece fibreglass frame.
This photo of the mold gives you a better sense of the pre-hung-door analogy. The frame is in the foreground and the top is in the background.
The lifting mechanism uses gas struts to raise the roof. The roof raises on hinged, square steel tubing, with the top moving slightly backwards relative to the van due to the radius of the steel arms, much like a parallelogram. In the photo below, the steel arms are angled forward < // > and the gas struts are in the centre angled backward < \ >.
The inside height of the opened top is about 6'2"; I'm 6'1" so it works for me as long as I don't walk into the light or the smoke detector. Closed, there is enough room to sit on the rear bench with plenty of room to spare. The bunk does sit lower than in an SMB due to the frame being installed inside the roof opening. In the photo below, the original roof plane is where the aluminum molding is at the bottom of the fabric.
I really like the roof. It is fairly easy to open and close, although I will need to add a second set of struts when I install solar panels.
Hope this helps.