If you primarily crappie fish...
I would build it as low (allow 3 - 4" for pin pedestal) to the hull as possible. I have built / rebuilt 5 jon decks now on 14' to 19' boats. Used to like the high decks for bass. Now I'd rather have a low or drop down deck for crappie. I got 3/16" 4X8' sheets of diamond plate aluminum from junk yard along with some angle and C channel and mounted all with rivits. May be better if you gotta welder, but my last job hasn't come loose yet in 9 yrs of use.
The only time I like a high deck is flippin for bass, otherwise keep it low.
Early to bed, early to rise,
Fish like hell, make up lies.