. I have acquired considerable practice with cutting rough lumber freehand on a table mounted circular saw
, without a riving knife or splitter.
You did not mention using a fence.
Here's some free advice. Do not cut lumber "freehand" on a table saw. It's not like a circular saw. A table saw is designed to ONLY be used with a fence when ripping... it's called a rip fence. IF and WHEN the blade binds because the wood closes on the it or when the edge of the work is not held in contact with the fence it will bind and a kickback will occur.
Only wood that been straightened on a jointer is designed to be place against the fence for this reason. You can use a board straightening jig to make the rough or curved edge straight THEN use it against the fence.
If you want to straight line rip rough lumber.... use a track saw, not a table saw. Instead of making a table saw from your Chop saw, make it into a track saw, and work from above like using a circular saw with a guide. A track saw will follow the "track" or guide, NOT the rough edge of a piece of crooked lumber... no binding, no kickback. It will be much safer!
The track saw won't allow the saw itself to meander or change course, since it's confined in the track, NOT just held against a guide by the operator. It's like a circular saw on rails, and there are larger versions called "rail saws":
The famous lawsuit by an unskilled operator against Ryobi who was ripping flooring freehand on a small table saw and lost some fingers... I don't know all the details, but it cost Ryobi 1.5 million $$$. The jury blamed the saw manufacturer, when it was clearly the faulty of the operator who did not have any of the safety guards on or was not using the fence.
The issue I see with re-purposing a chop saw it that it will not have a self-retracting blade guard unless you account for that in the design. You will have to be extremely cautious when setting the saw down with the motor/blade still spinning, since it will grab and want to come backwards. There are issues either way... track saw vs table saw. You must be aware of these before making any home grown versions of either.
EDIT: For "freehand" ripping of rough edged wood a bandsaw would be the safest machine or a jigsaw.....