How do you look for the spine on a two pice rod? Each piece individually? Or does the butt section even matter because of its stiffness? I've only built one piece rods until now and have never had to think about it.

You should locate each effective spine individually and then join the two according to your markings. When you join them the effective spine may be found to now be a very few degrees off. That is okay, remark and proceed with building the rod.

Butt sections can be a pain to spine. Yes they are stiff and don't like to bend. A vertical spine finder is the more effective tool here. In the event that you cannot locate the spine, sight down the blank and locate the natural bend of the rod. Mark the outside of the natural curve as the effective spine. This won't necessarily be right on it, but it'll be close enough to work well. As you suspect, the top half will have the greatest effect and is the most important.

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DO each piece seperate,mark and put them togather then do as one piece, hope this helps you Ken