An update, here I acquired a modulator that includes an S-video input jack. So I installed the above circuit to it.
And a snap of a notch filter TV fed by this s-video modulator mod:
Notch filter TVs usually have color crawlies on sharp luma edges, but as I filtered those out in the luma before it became composite video, these are way down or not visible.
This modulator uses a LA7161 chip, and it can be configured to do Japan channels 1 and 2, which happen to be identical to American CATV channels 95 and 96. Because I can.
And this allows me to have multiple modulators running at the same time.