Gaming or GPU render? the system will follow the slowest speed, so you should find out how fast the reference can go and than match the SC to it. Assumed the reference occupy slot_2 in SLI, without manual adjustment (EVGA precision) your SLI will run according to slot_2 speed.
Never hand on the EVGA reference nor SC but you should check what VRM+choke+video memory chip they use, if they are identical, there'll be good chance the reference will match SC speed. You can do hybrid cooling to achieve optimal result.