Planning Strategy 52 with a Phantom Material

Here is the issue form the following scenario.

I have a finished good & semi-finished good that are not made until an actual sales order is created for the finished good. I forecast at the finished good level to drive procurement of the raw materials so they are on hand when orders are dropped. In the scenario, we have a variety of ways to create the semi-finished good. In order to overcome this issue, I created phantom boms that consist of the different make-ups for the raw material that goes into the semi-finished good. I am currently planning the finished good with strategy 52 (planning without final assembly, non-make to order) and letting that strategy drive for both the FG and SFG. However, since creating the phantom materials, procurement for my raw materials is no longer being driven by the forecast, they are now being driven when actual demand comes in. How do I allow forecast demand to drive down through the phantom to the raw material? Please advise.

Thank you!