some more tests with Danne's March20 build
I followed the instructions from Danne ->
https://www.magiclantern.fm/forum/index.php?topic=9741.msg208959#msg208959so basically I started the cam with the new build on it, enabled the essential modules, formatted the card from canon menu, after restart I executed the "eosm cinema 2.35:1" script.
then in croprec submenu I've removed the 25fps and in raw video menu dialed down the res to 1136x1920 (which is fairly close to 16:9 ratio)
now, this is interesting - I've forgot to mess with the ratio setting in croprec submenu, so there was still ratio of 2.35:1 set. result was nice, only one corrupt frame out of 3100 and no stuttering or so.
then I've noticed I've forgot to change the ratio, so I changed it in croprec to 16:9 and recorded another two minutes. I noticed also after the ratio change, that res was corrected to 1136x2000, which is little less 16:9 then my set res before. viewing in mlv app, in this clip I've had 7 corrupt frames and stuttering in the movements, not that much, but it was there.
then I changed the preset to 2.5k and recorded at max res of 2192x1234 another 2 mins. no corrupted frames or anything else, clean picture at 24 fps.
so maybe its best not to touch the ratio setting after executing the script.
one is still a bit of disadvantage that even if I can push the crop a bit to the left with reg_skip_left
trying to move the crop up with the other reg results in bad image, so its now impossible to properly center the crop, which at this high res is not quite suitable for c-glass
will test further, thanks to Danne and others for this.