Looking at the side view of the bike, taking into consideration the need for extra weight in the forks, the weak link at present will be the area where the downtube welds to the frame tubes. It looks right. If you start adding there, addheft disease will spread. I have seen a 1,200 lb trailer built to haul a 200 lb bike...
Since you have drive torque feeding the front wheel, its got twist and extra weight. Your design looks well done to me, in fact without the extra braces on the forks it would surely be flimsy. I can imagine it would be hard not to throw 15 lbs of extra metal on there. Look at a radial aircraft engine mount made of tubing - its thin wall and there is lots of it.
No overkill there, it looks about right (TLAR)! Interesting build.
Jon