A standard drift rod flexs with the eyes facing up taking up the stress of casting and fighting a fish over the top side of the rod. A centre pin rod is designed to flex and take up the stress of casting and fighting a fish with the eyes facing down.
This is a bit of a bit of an over simplification, but if you are building a custom centre pin rod, you have to find the natural flex pattern of the blank before locating the guides.
This is a bit of a bit of an over simplification, but if you are building a custom centre pin rod, you have to find the natural flex pattern of the blank before locating the guides.