Don't forget that casting/retrieving them can be very effective, too. BK has good tips, and for the water I fish I usually flatline them too. I usually use 25-30 lb. test, and I've needed it several times. From my experience, dropping water after a blast of rain is the best time to use the Flatties/Kwickies. If fish are heading upstream and jockeying for position and you drop a Kwikfish in amongst them, it's going to get clobbered.

Just goes to show that there is more than one way to skin a cat, and I wouldn't be surprised if all the tips above are effective presentations.
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She was standin' alone over by the juke box, like she'd something to sell.
I said "baby, what's the goin' price?" She told me to go to hell.

Bon Scott - Shot Down in Flames