MPS planned quantity to include QC sample requirement

I may be having a blond moment here, but I can't seem to work out how to solve this issue.

Some of our items require to be produced in slightly higher quantities than needed. Eg when a quantity of 5kg is needed, the work order needs to be raised for 5.5kg. The 0.5kg is for a QC sample.
Shrink, yield and scrap settings only seem to increase the quantity of the components.
The planning message is still going to be for 5kg regardless of any of the shrink/yield/scrap settings.
How can I configure JDE to create an MPS planning message for a quantity that is 10% higher than required?

Thanks in advance for any suggestions,