Never mind it did work. And it did fix the "landing on invisible platform" issue. Combat is also fixed!
I missed adding a space between the property and the value. (I had "-screen-height480" and not "-screen-height 480" without quotes of course)
I also assumed (foolishly) that it would make the window smaller, not lower resolution.
Anyway thanks again for the SOLUTION! And looking forward to fully playing! :)