I've heard that about Boltz Lake ... lots of Crappie - mostly dinks.

I don't know if Williamstown Lake (near Dry Ridge, KY) or Bullock Pen ( a little farther North of Boltz, off I75) are any better for size of Crappie. Or even Corinth Lake (about halfway between G-town & Boltz Lake, on I75).

BUT ... if you don't mind driving an extra 20-30mins each way, I'd suggest going to Taylorsville Lake. The last two years fishing there, have been very productive on Black Crappie & White Crappie in the 11-14" length range ... and in good numbers, too.
Just remember ... the size limit is 9" & the creel limit is 15/person/day. And don't forget ... your 2016 license expires this month.