we send a notice to the customer 45 days prior to expiration date of the flood policy
Unless you have a Forced Placed MPPP policy in place, you can't start your force placement procedures before the policy expires. You can remind them their policy will expire, but the "45 day clock" doesn't start until the policy expires and then you notify them.
If they have $30M in hazard insurance, why do you they have $70M in flood insurance?