@redguy_ I haven’t yet noticed any notable downsides compared to all the benefits. Averaging is probably not a good idea, as 1-2 of the samples end up being taken on source dot boundary and thus are fuzzy/unstable. I made the implementation so that upper bits of phase select control which sample of the sets of 4 (320×240 mode) or 5 (256×240 mode) are used, and lower bits control TVP sampling phase.
@paulb_nl Yes, H. samplerate should be then set to 5x source dot rate when using 256×240 mode. H. active, H. synclen and H. backporch values are still shown/set as before, and multiplied by 5 internally.