Set the Product with a custom widget

Summary:

"$Incident->Product->ID = 3907;" States is read-only.

Content (required):

We have some complicated forms and are trying to sort them by product. We have a rather long line of code that does work but the part that doesnt work is, "$Incident->Product->ID = 3907;". This sits in the controller and after our incident is created, we set all the fields and this will not save, saying product is "read-only". Is there ANY way around this. Is their any way to manipulate the form submit widget or change this from read-only? If not, is there a better way we can bring in forms so that they can be reported on and filtered?