I had similar problems with my lt-1 in the Z. I eventually went to a surge tank and second pump to feed it and the fuel starvation problems were solved. I tired a fuel cell with a sump and foam but on the track with less that half a tank, I had problems.
I don't know how the 280 tank is baffled but I would be supprised if it was baffled enough to solve you problem.
As for the fumes, if you vent the tank straight to the atmosphere, try to run the line higher than the tank with a loop in the line and then the opening back to the level or below the level of the tank. This helped with fumes from my cell but did not totally solve the problem.