I separated my house bank from the starting battery years ago, and the Gp 24 start battery gets my Atomic 4 going just fine. A combiner (voltage sensitive relay) connects them together for charging.
After a few years that way, I did change the alternator output to go directly to the house bank. Seems the start battery never really discharges, and often my alternator controller saw full charge and dropped out before the VSR closed (it has a time delay).