A buddy of mine — Tom, runs a small range outside Lincoln — pulled a Mathews V3X out of his case last summer with a quiver of arrows that ended a quarter inch past the rest. Clean. Fast. Shot like a knuckleball past 50.
He'd let his pro shop cut them "the standard way." Which usually means: as short as physically safe, plus a hair for buffer.
Wrong way.
Why shops cut short
Two reasons. Both bad.
Speed sells. Shorter arrow is a lighter arrow. Lighter arrow puts more fps on the chronograph. The shop wants you walking out impressed by the IBO number. You asked for 290? They'll get you 290.
It also looks "right." A 30-inch shaft hanging two inches past your riser at full draw looks weird in the shop mirror. Customers don't ask for it. So nobody offers it.
Neither of those reasons has anything to do with how your arrow actually flies.
What you give up
A longer shaft is a weaker shaft. Same spine number stamped on the box. Same tip weight. Dynamic spine drops anyway because the shaft is now a longer lever.
That's not a flaw. That's the lever.
Hunting builds want point weight up front. Bigger broadheads. Titanium inserts. Higher FOC. Every one of those weakens dynamic spine. If you started at the bare minimum cut, you've got nowhere to go. You're stuck on a 350 spine Black Eagle with a 100gr field point, and the second you thread on an Iron Will Wide 125 — which is what you wanted to hunt with in the first place — the bareshafts start drifting left and you don't know why.
You do know why. Spine is now wrong for the build, and you can't shorten the arrow more than you already did.
If you'd cut it an inch and a half long? Trim a quarter, retune, done.
Length is tuning latitude. The pro shop traded it away for a couple fps you didn't ask them to chase.
The real cost
Yes, a longer arrow is slower. About 3 fps per inch on most setups. Closer to 4 if you're running a hot cam like a PSE Sicario.
Call it 6 fps off your IBO. That's the entire penalty.
You will not miss 6 fps in the field. You'll miss it on a chrono in front of your buddies. Every animal I've shot with a bow doesn't care whether my arrow was doing 282 or 288. They care where the broadhead landed and whether it was sharp.
Six fps for a fully tunable arrow you can rebuild for any season, any broadhead, any animal? Take that trade every time.
How long is "long"
Rule I use: at full draw, the broadhead tip sits even with the front of the riser or up to half an inch past it. Not flush with the rest. Not flush with the cable guard. Flush with the front of the riser shelf.
Most guys at a 28.5" draw: a 29" to 29.5" finished arrow on a typical 6.5" deflection compound.
28" draw: 28.5" to 29".
30" draw: 30.5" to 31".
You can always trim more. You can't uncut.
How to do it at the bench
Mount the rest. Come to full draw. Mark the shaft where it crosses the front of the riser. Add half an inch. Cut there.
Spine it. Bareshaft tune at 20. If the bareshafts kick stiff — left for a righty — pull a quarter inch and retune. Repeat until bareshafts and fletched arrows hit the same hole.
Start long, you converge in two or three cuts. Start short, you buy new arrows.
That's the pitch. Longer arrows are forgiveness on a budget.
If you want to see what your dynamic spine actually looks like at different cut lengths — what happens when you go from 100gr to 125gr up front, or thread on a 30gr titanium insert — run the build through The Forge. Drop the cut by an inch. Watch the deflection number shift. Then go to the bench and cut once.
Cut long. Tune the rest.