I would like to build some new wood arrows  @ 29" bop , for a 53lb r/d longbow. If I were to use 125gr woody weights and 125gr heads for a total of 250 up front , how far up in spine should I go on the shafts? The bow is cut to center and has a b50 string. I draw 28" and this bow is right at 53 lbs at my draw length.

60-65s should get you close

When you make that much of a change, it really pays to paper tune with some test arrows.  The formulas are just a SWAG at best.  For me, it seemed to take one pound of spine for each 5-7 grains of point weight.  It also seemed that the increase in spine slowed down when point weight went over 200 gr.  From 200 to 300 gr point was only a few pounds spine.  I think depth of shelf cut can make a difference, too.

I would SWAG at 80-85#, maybe 85-90#, but I have not had positive results with a lot of weight up front on woodies.

I personally like 145-160gr up front on my woodies and have very good results.

B50 string and 1" longer I'd try 55/60 first because believe it or not a lot depends on the side of the shelf on the bow riser and what the strike plate is doing.  55/60 or 60/65's should be about right,,,,, if you went FF and depending on the bow maybe bump the arrow to 65/70

Either 80-85 or 85-90

When I used to shoot woodies out of my 55# bows with 125-145 grain BH's I shot 70-75's ... since you are adding woodie weight also, I would agree with the guys on 80-85's ... with wood I believe it's always better to error on the high side of the spine chart.

Good Luck to ya

With the set-up you describe, 60-65 lb. spine would be a good starting point with 125 grain field points. Adjusting for the added 125 grain "Woody Weight" and using the "rule of thumb" 5 lbs. spine weight increase for each 35 grains point weight increase you should be close at 80-85 lb. spine wooden shafts.

That's a lot of weight up front for a woodie. Even with good flight your range will be thwarted by a big arch!

I'm shooting 60-65 # tapered Sitka spruce cut 28.5" BOP with 125 grain woody weight and 125 grain point from a 1958 Kodiak . 52# @28" with b-50 string.  The fly perfect.  

Advice here will get you close but having test shafts around is the way to go. Everyone shoots different.  If you're a wood arrow coniseur with several bows or the desire for several,  do yourself a favor and get some test arrows in a multitude of spine ranges.  I made up my own with leftover feathers and attach the point weight I want to use. I just did a clear sealer over the natural wood grain AFTER I wrote the spine on the raw shaft in the middle with a black permanent marker.

I'm shooting 70-75# 29 1/4" BOP Surewoods with 165 up front out of a 52# Toelke Whip at 28 1/2" draw. They seem to fly well.  I agree with going somewhere in the 80# range for woodies.  I'm no guru, but the research I have done to get lots of FOC out of woodies seems like more trouble than its worth.   Let us know how it goes.

Just for reference. I shoot a Wes Wallace long bow that is R/D. It's 54# at my 29"draw. I'm shooting footed arrows that I make. The foots add about 65 grains to the shaft weight with that weight being up front. I shoot 160 gn tips. My bow tunes perfect with 70-74# spine. My shelf is not cut to center.
You have 25 more grains, center cut shelf, but b50 string. I would think a 75-79# spine would work well. If your under spined a little you could always build out your shelf.
The best thing would be to get a test pack and shoot them.

I shoot a longbow 50# at 26". (56@28)

160gr point (595 gr total weight)

And I use 60-65 douglas fir, cut at 27.5" to bop and they make a bullet hole on paper.

Go a little heavy and sand to fit your needs if you have access to a scale.