Barbs on the tubes out of the tank can be made by soldering a small piece of paper clip wire to the tube, make sure you do the clunk inside the tank as well. Also make sure you don't leave behind any sharp edges that would cut through the tube.

Vent line needs to go over the top of the tank before exiting the fus to stop fuel from syphoning out in manouvres.

I personnally don't like the T connection in the feed line as it introduces another joint that could suck in air, I have also found that the commecially avilable fill valve sealing rings break up in time and allow debris into the carb with obvious results, I always use a dedicated filler.

Mike