US Open Cup - Substitution Rules?

[ej_dad]

Last night both Dallas and L.A. used 4 subs.

Are the FIFA substitution rules modified for US Open Cup games?

Are their any other FIFA modifications for US Open Cup games?

[AndyMead]

What FIFA substitution rules. FIFA only mandates substitution limits for its own competitions. I know the early USOC round games involving the PDL Raleigh CASL Elite has a limit of 5 substitutions.

That's not a "modification", it's a "rule"