I've followed the valuable information on this link:
The situation that I'm analysing is very similar.
I have one material, that we are going to call a pack. Instead of selling a a pair of shoes and a pair of socks and paying them both, we are joining them in one material ID and sell it with some discount.
So, I have material X, that in fact is a ID to join two material Z and Y.
The material X will not be managed in stock, only Z and Y, but when creating the Sales order, when entering the X, it will explode (and it is already!) and display also the Z and Y. In the SO, only the X will have price (the billing price), but will not have stock. In this case, wich category item to use? I've already used TAP and TAQ, and I'm using in MM03 this top material as ERLA, but without success.
For the bottom items (the components of the BOM), I'm using TAE and it seems ok.
Also, when creating the delivery, the idea is to have picking for the components, but the top item (BOM ITEM), as it doesn't have stock, it doesn't have picking. When billing, it will pick the price inserted in this bom item, not in the sum of the components.