3 rivers online dynamic spine calculator wrong??

[Elewis]

Please help
Is this thing (3 rivers dynamic spine calculator) of any use.  I am somewhat new to archery but I am pretty sure this thing has some aspects that do not work correctly.  

I was trying to see what my planned arrow would work out to versus my Bear Grizzly's spine requirements.  The arrow shafts that I am getting are Forrester wood shafts which are made from a hardwood.  They are footed arrows. When I make the adjustment for the footing instead of having a slightly weaker dynamic spine which is what I was expecting I got an arrow that suddenly had a 40 lb increase in dynamic spine.  

Perhaps I somehow entering the information incorrectly

I have a 50 lb Bear Grizzly recurve and a 29 inch draw. -0.125 center with a strike plate

The arrows are 5/16, 57-60 lb and footed to 11/32 at the tip.  They weigh about 430 grains (shaft).
-They will have 125 grain Brodhead and 3 5.5 inch feathers.

3 rivers says they have a dynamic spine of over 90 ??

[JamesKerr]

Any time I have tried to use 3 rivers spine calculator with wood shafts or other carbon shafts not listed in the drop down menu, it does not give accurate results. Try using Stu Miller's, his is the original and in my opinion is more accurate.

[Elewis]

Thanks for the quick reply.  I have a feeling that my current plan will work well.