Yep , all that piping work is custom . Mine has the original factory bow rail and it's nothing like that at all . It also still had the 2 tiny grab rails on either side of the console .
One of the deceiving things about the St T is its scale . When you're in the boat , especially when it's in the water it has a surprising amount of space for its size. But when you look at the boat from the outside when it has people on board it hits you that it's really pretty small . IMO all of that large pipe work that was done is out of scale to the rest of the boat .
Look forward to your findings .
It just occurred to me that if you have a 2 tank boat there should be a 3 way valve in the engine room , more than likely on the inside of the stbd stringer .

For reference you may want to check out this ad that was sent to me by one of the guys on the Donzi.net (thanks Greg)
I'd say that all of the rails on this one were added after it left the factory too .

7136172530.html


I notice that the one for sale (above link) has a fuel tank vent on the port forward side of the hull (like mine does) , unfortunately the pics you posted only show the stbd side of the boat BUT both boats have what appears to be a sight glass port on the floor in front of the lazarette . To me that would possibly verify that both boats have a forward tank , so in yours there should be another one under the console.
Also the 7th picture in this ad shows a rear view of the console and on the port side floor you can see what appears to be a crack in the area that I previously mentioned.