carbon arrow footing question

[stickum]

When you add an alluminum foot to a carbon shaft does it weaken the spine?  If it is longer than the insert does it stiffen the shaft?  Trying to figure which shaft to go with and this info will help.  I got a new long bow 49lbs @ my 28" draw.  I have some MFX Classics 400's from a my recurve and a 30.5" featherd shaft with 145 gr tip hits dead center where I am aiming at 20 yrds but the bare shaft is showing to stiff.  5 to 6 inches left of fletched shafts.  These arrows are 14% FOC and the local stores only have 125 tips and lighter.  Trying to figure out whether to go to 500 spine or if I can tune these.

[CoilSpring]

In General,
Footing same length as insert will weaken.
Footing longer than insert will stiffen the weakness caused by it's extra weight.

I think a 500 shaft would tune better with your 125's and footing, but it would be cheaper to order heavier tips/heads and tune your 400's with shorter footers.

[JimB]

I use a 1" footing on the front and 1/4" in front of the nock.The two come so close to cancelling each other out,that you won't notice a change in tuning.As long as you are doing it,protect both ends.

[stickum]

Thanks, these are some old classics that I won at a 3d six or seven years ago.  Just talked to a guy at cabellas and he said that the new classics come with adjustable weighted inserts from fifty to seventy five grs.  That should make the 400's work I think.  The 30.5" bareshaft with 125 grain tip hits about 6" left of fletched and the same shaft with 145 gr tip is 3-4" left of fletched.  The 145 gives me 14% FOc, so between full length arrow and wtd insert do you think the 400's will tune?  (rt handed shooter)Cabellas has fletched half dozs of 400 and 500 in stock.  I will buy a half doz to tune, but still not sure whether to go with the 400 or 500.