[C320-list] Shorten Upper spreaders for 155% genoa trim?

[Glen]

In racing a C 320, the 155% genoa seems to perform to weather best when trimming the sail until the leach touches the upper spreader.
 
However, once it is contact with the upper spreader, moving the genoa sheet block forward does not help keep the upper third of the genoa from luffing before the lower third.  It appears that the only way to get the whole luff to perform would be to shorten the upper spreaders by about two inches.
 
While it seems for lake sailing in moderate winds this would not put the rig at risk, I'd be curious to hear if anyone has done this, which end of the spreader they shortened, and any other comments on genoa trim to weather.
 
Thanks,
 
Glen McIntosh