Thanks paulb_nl. It looks like the changes allowed for a larger H. active area for 320×240 optim. mode.
I found a quirk that normally doesn’t appear when using generic scaling, and it’s related to setting the active area well above 512 while keeping the sample rate fixed at 682. I guess a screenshot would best illustrate this problem (point scaled up to 2208×1568): https://i.imgur.com/5eILBOx.png
In this case, I set the active area to 552 (Cam Link outputs to 1104×480). Normally, the H. active area will just expand to have more open black space on the right-hand-side of the video, allowing for backporch adjustments to move the image to the right. However, it looks like the extra space on the right-hand-side is a copy of a portion of the SNES active area. The right side of the video gets cut off as I increase the backporch, so there’s an invisible barrier and I have to keep the image as far left as possible. I don’t know if its just a problem with the Cam Link, but I figured it was worth mentioning. Other than that, it works nicely when scaled down to 256×240.