I have never had anything to do with cutting Jarrah. How does it compare with Red Gum? What do you regard as "a small petrol motor"? I would be thinking about the shaft of that small petrol motor and how much it will resist twisting and snapping. Do you have a reduction gearbox to use?
I have always cut firewood at about 300mm lengths where possible. Both of our stoves could take 500mm lengths, but I don't think the hassle of splitting 500mm of Red Gum is worth it. My splitter (Homemade) lifts the wood to working height.
This will be interesting to watch if you do continue. I have no idea about whether it will work with your timber, but I suspect you may be asking a bit more effort from the device than those rednecks were. I have seen either this video or a similar one before. I remember this topic being discussed before, on the forum I think.
I don't think it would work with the knarly Red Gum I see. It often needs splitting all the way thru, resisting to the very end. 220mm of action would see a still solid lump of partially split firewood.
Dean