I know I am close!  Thanks for great advice.  I have gotten rid of all weather helm, and now need to fiddle a bit as I think I can point a bit better.  All this is for 3430 a Douglass built beauty with older (2005?) Shurr sails - loose rigged.
I am showing 28' 7 1/2" accurate using correct measuring from Mast Head to transom.  My Forestay has the slack taken up, I suppose you would say.  When I put my Loos gauge ( the good one ) is may show 30 pounds, but there is noticable softness in the forestay.  (of course measured with zero tension on the jib halyard, thus the Lever pulled up on the left side.  My side shrouds have a bit of tension on them and they measure 100 pounds on each side.  All measurements taken with the boat in its wet slip, boom on, no sails.  Temp. at 90 degrees.
I could figure out how far to tightent the side shrouds so that I would get the 3" shorter dimension from Mast to Transom lip, but darned if I can find a scale drawing or complete list of specifications.  I am even doubtful of the published mast above waterline dimension of 28'-0"  I think this is substantially wrong.  Does anyone have the correct length of the mast?  I could easily measure this, but am half hour away from the boat.
So, if I tighten my shrouds, I'll need to loosen the Fore-stay. 
Any suggestions to my puzzle?  I am fearful of making this change (lowers the boom tip) and that seems to me to add weather helm back...