For my pre-employment test I used Magnum Sythetic urine after talking with the local headship guy, I live in a SMALL town, he said there was one person at the testing facility who has caught a couple people using synthetic by actually smelling the samples
If that "person at the facility" had any real background in human biology/urology, s/he would understand that a lack of odor can be exhibited in human urine samples as well as synthetic.
S/he would also understand that it is improper to flag a urine sample on the sole basis of odor without first running the appropriate validity tests on it.

Dont add anything to the QF. If youre really all that worried about odor (in which you have no reason to be), then why not just use all of your stored clean sample?