I'm hoping to shoot cedar arrows from my 50 @ 28 Pittsley Predator recurve. I draw 28". I want to end up with a 125-150gr broadhead and a 30" bop arrow. I tried the spine calculator but was unsure how to enter the correct wood arrow selections. I came up with 70-75? Does that sound right? Thanks in advance.

50@28 +5 (recurve) +5 (center-cut) +10 (2" pass 28") Yes 70-75 sounds good.

Wood arrows can be funny things - they can be sensitive to your rest and release style.  I'm drawing 30" on a recurve marked 52#@28" (so, figure 56# or so at full draw) and it prefers cedars of 60-65# with a 125gr head.  It's cut a little past center but I build it up with a furniture rug pad sliced thinner with a single-edge razor.  

I also have a bow marked 55#@28" and that one prefers 65-70# shafts (same 30" draw w/30-1/2" BOP shafts with 125 gr heads).  And a bow marked 48#@28" that prefers those same 65-70# shafts.  

One spine range will shoot where you are looking and give smooth flight.  That's the one to use regardless of what a table says.

Some insurance company has a table that says you'll live to be XX years old.  It's based on historical averages.  Your results may vary.

It usually works with a deep-cut shelf to err on the side of heavier - but not always.