ok this is a two-parter...
10.a we need OPTIONAL parameters when creating InstallScript functions.
10.b. we need to be able to pass a param to an InstallScript function from a Custom Action.
Why, you ask? Well... either would suffice. If I could supply a default value to an OPTIONAL param in an IS function, then I could (in theory) call it from a Custom Action (which currently doesn't support passing params to IS functions).
Is there a workaround? Well yes, of course... I just write a wrapper function that doesn't need a parameter and call the function that does need the parameter. I call the wrapper from the Custom Action. But lets be honest, that's kinda kludgy.
C.