Currently, you can effectively only specify one flow rate bracket per sewer pipe size per sewer pipe slope since the number of sizing inputs is fixed. This doesn't allow for the end user to take advantage of their local building code allowing different flow rates for the same sewer pipe size at different slopes. For example, there might be an instance where the design requires a 150mm pipe at 1% slope but elsewhere in the same design another instance that requires 150mm pipe at 1.5% slope.