I'm making 12 foot overhead on a 4 wrap medium taper fibreglass blank.
Overheads on such soft rods are prone to turning under load if the spine is not accurately chosen.
A quick palm roll suggests that my blank has two 180 degree opposed spines.
Do I want to use the weaker of these two spines? My plan was to affix the rod and attach a small weight to the end and test which spine bends the most.
My guides would be placed on the outside of this bend (being an overhead).

Again, Do I want to use the weaker of these two spines?
Regards,
Adam

We just got through with this! Read the comments on this topic 13 posts below yours. In my opinion spine is of no consequence, but others believe otherwise. I build on the straightest axis. Read the comments below and make up your own mind, then do it your way.
Norm

Adam,
At the risk of seeming unconcerned, 2X Norman's reply.

Mark Talmo
FISHING IS NOT AN ESCAPE FROM LIFE BUT RATHER A DEEPER IMMERSION INTO IT!!! BUILDING YOUR OWN SIMPLY ENHANCES THE EXPERIENCE.

You can read all the posts on this subject and you will not be any closer to a solution than you are now.

You will get conflicting and accurate advise to your question, Many of the responses are based on personal experience and preference, some are based on experiment. You have to digest all the information and make your own decision.

The choices as I see it are.......

Go with the advise of the responder you have the most confidence in or rely on your own experience to select the axis that best will respond to your needs.

I will pass on offering an opinion to this post because my position is clearly and consistently stated in previous posts.

Have fun

Thanks guys..
Reading it now

When you get done with that, if you would unhide your email and you will find some more reading...

Adam,
Make your job simple.

100% ignore the spine of the rod blank.

Roll each rod section and mark the straightest axis on each section and build the rod.

Just forget about spine and enjoy rod building.

Be safe