If you're at .028", I'd close it to .020" and test it out. If you are in fact blowing the spark out, the money required to fix the problem would be better invested in a beefed up ignition system rather than re-cutting the head IMO.
With the forced induction cars we used to build, we'd start at a gap of .010" and go up incrementally by .002" until we saw a miss. At that point, we'd back it off by .004". Some instances allowed for .050" or more, while some didn't allow for more than .016".