I use a similar rig for blue gill & Perch when they are deep. I use a set up similar to yours for long lining Crappie, I use a 3 way & a short drop @ the front jig, usually around 18" apart for the the back jig. Mainly use soft baits on 1/16 to 1/8 jig heads. This works best when fish are in 10' -
20'. Experiment with length of line out. I will cast out, then make sweeps with the 10" rod 180 degrees with the bail open.
I use 6lb. mono, & the rig made with 4 lb. florocarbon. i use split shot on the main line if I need to get deeper.
Normally my boat speed is 1/2 to 1 1/2 mph. My fish usually are on the rear jig.