The Scale Shipyard's nuclear subs come with these index strips included, they are made to match the radius and contour of the hull.
I find that the strips are superior to molding in an index lip into the hull, as these are just on the lower half of the hull, there isn't much to keep the top half of the hull from spreading some and sliding down over the bottom half.
This can happen with both Polyester and Epoxy fiberglass hulls.
The modeler just needs to cut the stips in several pieces and then attach these to both the top and bottom halves of the hull, alternating as you go along the length of the hull, you can adjust where you put these to suit your internal installations if required.
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