Right now I'm shooting 60-65 Rose City POC's with 125 zwickeys up front.  I'm wanting to try Surewoods with a little heavier head preferably ACE express 165's.  My main question is do you think I need to bump up to 65-70's or 70-75's.  I need a 30.5" arrow.  I figured someone around here would have some sort of knowledge of bumping up a spine group for every so many grains up front.  
Thanks,
Ben

I did just about what you are saying. I was shooting 55-60 spine with 125 grn BH and wanted to go with a 160 grn Ace for my hog hunt last spring. 60-65 worked fine with the heavier head. My arrows were 28" BOP where you need 30.5. Don't know how much difference that would make.

It is borderline.................if you go with 65-70 and they are weak you could slide a match under your sidewall since going shorter won't work. If you go to 70-75 you have maybe a half inch of shafting to make them act weak if they are stiff. So I would go with the matchstick under the sidewall if need be and the 65-70. But the best is to get a couple of each and check it out.

Thanks guys exactly the info I was hoping for. I could get by with a 30 " in case they show weak

As always, good advice Bjorn.

You might get a couple of "test arrows" and see for yourself which works best for you. I can help with that if you'd like.
 
 David