Convert from Fixture unit to L/s using Dynamo

I am trying to do edits in flow conversion method in Revit, Revit is using IPC 2012 tables in the conversions from Fixture unit to L/s. In flush tank systems there is no problem, the problem exists in flush valve system.

Revit converts any value below 5 FU in flush valve system to 0.95 L/s even if this value is equal to 1 and this value “0.95 L/s” for 1 FU is very very high.

I was trying to do a conversion for flush valve values less than 5 FU in flush valve systems to be similar to the conversion in flush tank system. I did that using Dynamo as per the below photo, but the problem is the “Flow” parameter is read only parameter.

Can anyone help me in this issue by using Dynamo or by another way?

Thanks in advance.

Any body can help !