No idea about harmonics mate but I reckon 5 bars might be a bit over kill, probably only need 4 max. As you've said, move the first bar above the B post, keep the last one where it is, and spread the others. Shouldn't have to move the platform back too far at all really. May just move the U-clamps in slightly along the bars first, so they're not fixed right at the edge of the platform, that way the mesh part is less likely to vibrate against the bar.
Guess it's all trial and error to see what does and doesn't work