Maximize is a strong word. Let's try improve or to optimize the settings for low salt use but good softening. 4 lb per cubic ft of resin would use less salt, but it would not give such pleasing water.
This presumes BLFC=0.5 which is the most common. Note your current C and BF settings. If they are much different than those in the table below, let us know. This also presumes no/very low iron. If significant iron, DO should be set lower.
System info (not programmed)
salt lb/cuft = 6 ; A choice ( efficiency vs capacity)
BLFC = 0.5 ; Brine Refill rate GPM
cubic ft resin = 1.5 ; ft3 resin = (nominal grains)/32,000
Raw hardness = 25 ; including any compensation
Estimated gal/day = 175 ; 60 gal per person typical calc
Estimated days/regen = 6.9 ; Computed days ignoring reserve
Fleck 5600SXT Settings:
DF = Gal ; Units
VT = dF1b ; Downflw/Upflw, Single Backwash
CT = Fd ; Meter Delayed regen trigger
NT = 1 ; Number of tanks
C = 30.0 ; capacity in 1000 grains
H = 25 ; Hardness-- compensate if needed
RS = rc ; rc says use gallons vs percent
RC = 175 ; Reserve capacity gallons
DO = 28 ; Day Override
RT = 2:00 ; Regen time (default 2 AM)
BW = 5 ; Backwash (minutes)
Bd = 60 ; Brine draw minutes
RR = 5 ; Rapid Rinse minutes
BF = 6 ; Brine fill minutes
FM = usually t0.7 but not always; flow meter, make note of what is there
If you want to try other settings, where the settings in bold are in the good-compromize range.
BLFC = 0.5
cubic ft resin = 1.5
lb/cuft ; C= ; BF= ; salt efficiency (grains/pound of salt)
4 ; 22.8 ; 4 ; 3800
5 ; 27.3 ; 5 ; 3640
6 ; 30.0 ; 6 ; 3334
7 ; 33.1 ; 7 ; 3148
8 ; 36.0 ; 8 ; 3000
9 ; 38.5 ; 9 ; 2853
10 ; 40.5 ; 10 ; 2700
11 ; 42.0 ; 11 ; 2546
12 ; 43.1 ; 12 ; 2396
So using this table, you could change C to 27.3 and change BF to 5. That would be more salt-efficient than C=30 and BF=6. But there is a tradeoff in residual hardness.