Applying Lookahead with z3 Solver - z3

Question

I want to solve a CSP with the help of Lookahead method in z3 Solver. The issue I'm facing is not being convinced that it's invoked by setting an according parameter like s.set("sat.lookahead_simplify", True) or s.set("sat.lookahead.delta_fraction", 0.7).
Below is the code for solving my combinatorial problem. I ren a similar solver on a complex instance A and the runtime without these settings on Lookahead was 3674 seconds versus 3670 secunds with these settings. So, seems like they have no effect.
Does anyone know how to correctly invoke Lookahead here?
import numpy as np
import timeit
from z3 import *
def as_long(self):
if z3_debug():
_z3_assert(self.is_int(), "Integer value expected")
return int(self.as_string())
def model_int(mo, R, C, m, n):
R_int = [mo[R[i]].as_long() for i in range(m)]
C_int = [mo[C[j]].as_long() for j in range(n)]
return [R_int, C_int] # integer model values
def CSP(A, D, bit_length=8):
A_shape = A.shape
m = A_shape[0]
n = A_shape[1]
#initialize solver
s = Solver()
s.set("lookahead_simplify", True)
s.set("sat.lookahead.delta_fraction", 0.7)
#initialize column and row variables c_j and r_i as bit vectors
C = [BitVec(f"c_{j + 1}", bit_length) for j in range(n)]
R = [BitVec(f"r_{i + 1}", bit_length) for i in range(m)]
#initialize search space restriction constraints for r_i's as lists
Constr_D = [Or([r == d for d in D]) for r in R]
#initialize permit-constraints as lists
Constr_permit = [R[i] & C[j] == C[j] for i in range(m) for j in range(n) if A[i,j]]
Constr_npermit = [R[i] & C[j] != C[j] for i in range(m) for j in range(n) if not A[i,j]]
#add constraints
s.add(Constr_D + Constr_permit + Constr_npermit)
#search solution
check = s.check()
if check == sat:
return model_int(s.model(), R, C, m, n)
return check
# model instance ........
D = [7,11,19,35,67,13,21,37,69,25,41,73,49,81,82,84,88] #domain
m = 15 #number of rows
n = 9 #number of columns
p=.11
A = np.random.choice(a=[1,0],size=(m,n),p=[p,1-p])
print(A)
# executing solver on model instance ........
starttime = timeit.default_timer()
print(CSP(A,D))
print("The time difference is :", timeit.default_timer() - starttime)