I would say it kind of depends what type of plastic you intend fishing with and how you want that presented to the fish... If I was using the prawns I would use a HWS jig head and let it get up close and sink slow, but if I was using the grubs in 3" etc and would want it to get to the lower setion of the water I would go with a 1/4. I guess it really depends on a few things and what your trying to achieve with the presentation of the SP? hope this helps.