I'm shooting full length GT Entrada 600's w/125gr field points from my 41# A&H CX.  They are the perfect spine and fly like darts but only weigh 330gr.  Is there a heavier carbon shaft that will spine as weak as the Entrada 600's?  I would like to get to at least 400gr.  Does anyone have an idea how much point weight I would have to use to bring a full length 500 spine down to the 600?

Full length (29") Carbon Express Thunderstorm SEs with a 125 grain tip would probably work and they would scale at 395 with 3 feathers. You might need to or be able to use a 145 grain tip to get over 400 grains.

If 29" is full length they won't work.  I have to have 31" to shoot broadheads.  I'm drawing a little over 29".

The entradas are only 30" (shaft itself) where many of the 500s come longer.A beman venture 500 or ics hunter left full length would work and give you more weight and you might could shoot a heavier point.I use 500 beman ventures cut 30" with my 42lb bow.Gives me roughly a 440gn arrow.I can shoot the full length entradas with 100gn points from the same bow if that helps.

You could also just try some weight tubes.