Any wood will vary in weight for a given spine. If you haven't already, I suggest you contact Surewood shafts to see if they can provide Doug fir in the physical weight you want. If not, you might try Sitka spruce offered by Hillenbrand. Sitka spruce tends to run a little lighter than POC, but again, they should be able to provide shafts that are the same weight as those you're using now. All that being said, I haven't had trouble finding 70-75# spines in 11/32 cedars. I do my own tapering though. If that's a shaft that really works for you, you might consider stocking up when you do find them. Good luck.