I know everyone says to test your first void of the day. I feel as though i should test myself at the same time and under the same conditions i would be tested at.
This is an incorrect approach to this. The human body is not some type of electronic machine that operates on fixed settings (thank god for that!!). As you yourself have understood, THC levels in the urine fluctuate during the day and daily as voiding sessions and fluid consumption (during the course of the day as part of maintaining normal hydration) fluctuates. For the most reliable results, it is urged that you use the first urination of the day when THCA levels are at their highest.

If youre consistently testing negative with the first urination of the day (regardless of line intensity), youre good to go.