Ok, I had some time today so tried the latest Hypseus - https://github.com/DirtBagXon/hypseus-singe/releases/
It seems to me, with the latest release, you can now get '-scanlines' working better (dependant upon your display resolution) by taking multiples of the dimensions using -x and -y.
640x480, 1024x768, 1280x960, 2048x1536 - seemed to work better on some displays
800x600, 1600x1200 - worked better on others
Also seemed to get different results in using the new '-nolinear_scale' argument too.