If you use just the host (/32) as the source the other IPs will not match that ACL, so you don't have to worry about them. But, if that customer server needs to access anything on your hub network that is outside of its local subnet, the policy will need to be modified... I'm assuming it just needs access to servers on its own subnet which would be L2 switched, then anything from this host that hits the L3 gateway would match and follow the ACL.