for open face reels, i use 300yd of 65# spectra backing. the type of target fish determines on how much top shot to put. (YT on a kayak i do 20yd... halibut or threshers i go straight spectra). if you want to cast... you might want to uni-uni enough topshot so when you cast... the knot doesnt interefere with your guides (i put around 150yd of topshot for casting yoyo irons).
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