I'm going to install a dieselgenerator in my Sun Odyssey 43DS.
The problem is that i dont want to drill an hole in my diesel tank for the fuel supply, the idea of installing a T after the racor is bad? The generator is going to suck all the diesel from the engine?
Also for the return diesel circuit i'm thinking of putting a T on the engine diesel return hose...
With the caveat that any design an be screwed up by getting details wrong, your description is exactly how my boat was built 30 years ago and it just works. You need to be sure of design details, like is the Racor sized large enough to handle the combined flow of both engines, and be aware that an air leak into the fuel piping of either engine will disable both.