Yeah at this point, I've narrowed it down to being 2 settings filesSplit screen is functionality from Android itself. The ms apk or any other FYT apk has nothing to do with that.
50%/50% or 33%/66% is determined by the layout set from the apk. Most apks only support 50%. Some apks have layouts that can work on 50% or 33%, or even other layout widths/percentages.
If you have a 33%/66% screen layout, you should be able to drag the separation bar to 50% and back again.
customs_appid.properties: appid=b99c74bae38c52ae token=2d3893452746535fef63a651
fyt.prop: ro.fyt.ccbwin=0 qemu.hw.mainkeys=0
and the addition of the new UI 190043002_com.syu.steer.apk this seems to allow the HOME, FM & AM keys to trigger the actual Home and Radio action within the old UI. Has nothing to do with the ms.apk (both files same)
The UIs I am playing with are 9853i OS 1280X480 Old UI 2019.11.28 \ 9853i OS 1280X480 New UI 2019.11.28.
Going to open both steer apk's within Eclipse and view the differences.