I am looking to make my un-cut carbon arrows longer but do not want to use aluminum over the shaft.  Before you ask - my arrows are full length at 30" Velocity XT and I truly need about 3" more.  

Has anyone found the proper way to inner sleeve with something other than a dowel that will not change spine or weaken the shaft so it is not huntable?

Dont think you are gonna find an inside fit.

The best thing I have found is longer arrows. lol    

Check out some black eagle outlaws.  they are 32.5" long carbon to carbon.

Such a problem that the arrow manufacturers will not make a proper length arrow!

Maybe some of the 600 or700 spine would fit. I used a old skinny shaft as an internal footing on a couple of GT's. I was trying to extend the life of a couple "stumpers".
Are you close to a public range? Usually the broke arrows are behind the butt or in a trash can. I know some of those get "recycled".

My wife shoots 600 and they do not fit. I know they have the same .246 ID as the 500 - 400 spine GoldTip so the outside has to be larger.

Any idea what you used?

Did you know that GT will take special orders for longer arrows? I don't know if they will do it for John Q Public, you might have to get one of their dealers do it for you and it might cost extra. I was recently told this by buddy who's family owns an archery shop.

I have footed Tracy's Easton Redlines with a Gold Tip 35/55. It is a tight fit but it went. That made her an incredibly tough stumping arrow.
Bill

You put the GoldTip on the outside of the Redline's?