I knew I was on the cusp of needing a stiffer spine for my given set up. I have been shooting full length ICS 400s with 100gr inserts and 150gr points from a Grizzly rated 45# @ 28". My draw is 30". I also use weight tubes to add 3gr/inch to the arrow as I want the heavier arrow to retain energy. I noticed that unless my release was perfect I would get a little wag.  Having a few other bows with lighter draw weight to use with the 400s, I buillt up some ICS 340s with the same components. They fly like darts and accuracy is more repeatable. Consequently, the bow is quieter to boot!  

Tinkering and tuning is half the fun, until I stick one into a deer one of these days.

Seems like you are one of the few that shoot a heavier spine.  I have been trying to sell a half dozen GoldTips in .400 spine without any success.
Seems like .500 is a more common spine size.
I can't recall the last reference to a .340 spine arrow.

Have you tried shooting a bare shaft?  It was an eye opener for me.  Also showed how much is covered/corrected by fletching.

I shoot a full length arrow and add a hefty front end to it so I could probably lighten the front up a bit and go with that but I prefer the weight and balance I have. Besides, gives me more to tinker with and sort through.

On a side note, whacked a nice doe this evening. With an inline though. Yeah, I know. Wrong forum. Lol!

I just confirmed the tune on my 64 inch Kodiak Deluxe that is 45 pounds measured at my 31 inch draw...340 spine Full Metal Jacket with 200 grains up front...a lot of it is the BCY-X string but I get perfect bare shafting with that bow and that arrow just as I did with a 2315 and a similar string...do  not ever let anyone tell you a Kodiak Deluxe is not a great shooting bow

DDave