Contribution Margin report by channel using PCA

I am attempting to create a contribution margin report by distribution channel using PCA. The idea is to keep Revenue and COGS aligned by the distribution channel that is on the sales order. I am finding that distribution channel pulls through into GLPCA for the billing document, but not for the material document. Therefore, I have a mismatch when I view data by channel (although not overall) because the distribution channel is not populated on the COGS lines. (GLPCA is being populated with the profit center, amount, etc. but not the distribution channel)

Can anyone tell me how I might be able to populate distribution channel on the COGS entries?

Thanks!