I've made a new version of the board, which I think I'll treat as my "official" contest entry version. It replaces all of the resistors with 0602 SMD versions, removes all of the wire jumper connectors, and redirects the input and output to a couple of chips for ADC and DAC (respectively) with I2C connections. I probably need to add a couple of pull-up resistors for the I2C wires, but there's room for that; I made sure of it. I just need to work out the best values.
Once I make that modification (and possibly others based on viewer feedback), I'll post that update and start editing the Details section to reflect what I've done.
PS: Based on a commenter's recommendation, I've downloaded and tried out KiCad. I'm having a bit of a learning curve with it, but I'll get used to it in time. For now, for anything I want to complete I'm going to continue with Fritzing, and then try to duplicate with KiCad until I get the hang of it.
(I'd actually love to see what any of my boards -- but especially the two connector boards -- would look like in 3D!)