The Elgato Cam Link doesn’t seem to capture the new 512×240 optim. mode properly; it looks like there’s a sync glitch every 1-5 seconds: https://i.imgur.com/R4882TE.png
The output to my PC CRT monitor looks perfectly fine though, but I haven’t been able to find any tweaks to stabilize it for capture. Previously, my preferred capture method was a pseudo 512×480 optim. mode, by using 320×240 optim. and upping the H sample rate to 682 (among other adjustments). The limitation was that it could go only as far as 510 H active pixels, but it was a stable image. In the end, it is effectively one vertical column of pixels lost in terms of normal 256×240 modes. I’ll have to stay with with that method for now.