I installed everything I wanted from my "list" and a few extras. The version of Cliff Hanger you used is fantastic, but it's too much for my Pi3B+. How did you create the framefile and is there one that uses a lesser video scale but still uses the Singe side as well?
The best approach would be to downscale the existing 1080p Singe video with ffmpegffmpeg -i cliff.m2v -an -qscale:v 4 -b:v 6000k -vf scale=1280:720 -codec:v mpeg2video 720_cliff.m2v
As your re-encoding there will be a slight loss of quality, but probably nothing you will realise due to to downsize in resolution in any case.
We keep the bittate high with -qscale:v 4 - See ffmpeg docs.
You can check the frames are equal, on each, after the recode with mediainfomediainfo --Inform='Video;%FrameCount%' cliff.m2v 36780 mediainfo --Inform='Video;%FrameCount%' 720_cliff.m2v 36780
See my Singe 2 porting repo for links on how to get these tools.
Each game incarnation has a different frame layout, so you can't really use a video from one game in another version without rewriting all the game frame reference code in the LUA. This is one inherent issue with Singe (which will have fan changes and tweaks), unlike Daphne where the ROM frame references will always be the same. It's better to keep the video with the LUA code. You then just have to deal with the means to distribute it like that, and the inherent consequences.
Provided you have a decent quality source, down-scaling the video shouldn't be an issue. So having the 1080p will always allow you to get the games running on lower spec hardware, with a little work. Singe overlays are written to work with source video resolution, but hypseus will try to align on the new resolution. Some games have options to move sprites around in the Service menu (9 in-game ).
Others, you may need to make minor alignment changes in the LUA (text editing - main.singe - spriteDraw(x,y,sprite[LIVES]) ).
This is Daphne, but see my Dragon's Lair on a Pi Zero (first Gen), using downscaled video, in the forum here.