Is a 340 spine okay for this setup?
 

27.5" arrows
28.5" DL
70lbs DW

Using Beman ICS 340's

My bow was set at 65# but everything was tuning left. So I turned it up to 70#. I'm going to try to tune again tomorrow and hopefully it wont be as far left.

I shoot the axis which is the almost same thing. I think you could have gone to the 400, I like the heavier shaft, and I get excellent penatration, all pass throughs even through the spine. You can go on the easton site and post what you have and the arrow you want to use and it will give you the spine you should use. If you get good flight then use it, your bow will love you for it.

Maybe stiff. Depends on the bow of course. But I would shoot 30" arrow with your setup for most bows 70lbs.

IMO, 340 would be almost an ideal spine to shoot depending on how aggressive a cam your bow has. If it's a softer cam you may be able to get away with a 400 spine, but a 340 should still be tunable.

I would have went with a 400.
Im shooting 60#
30Inch DL
28 Inch Epic Sts
100gr Rage 2

More info needed before any good guess could even be made. Bow model, point weight would be two more of the criteria needed. Also your main intention for these arrows , target , 3-D , hunting or any of the above.

Bow: Diamond Stud
Point Weight:100g
Purpose: Hunting

Your good . Use 125 grain tips , cut them an inch longer and use 100 grain tips

I ran the numbers through OT2 and the 340's showed just slightly high spine but the best for your setup. 400's showed really weak spine. If you ever want to go to 125 grain points it will still handle the extra point weight easily , so you are good to go.

Are you using a licenced version? My licenced version Ontarget shows not slightly but a bunch overspined. Only way to make it happen is to use 30". The unlicenced version won't take in account the bow much.