I finished writing the microcontroller code to read the GPS time and only start transmissions when the minutes value ends with a zero. The signal now stacks nicely in 10-minute grabs. Now that GPS and the oven is working well I've started sending my call sign (AJ4VD).
First spot occurred while I was actively adjusting the transmission length
5x frame stack (mean frame) from the WD4ELG grabber reveals the AJ4VD signal much better, and confirms the GPS timer is working well.