Jay: I have a White Outdoor ride on with 12HP Briggs on it's last legs.
It has 18x9.5 tyres on it, same tread pattern as these: https://www.outdoorking-forum.com.au/index.php?main_page=product_info&cPath=648_649&products_id=3737

Might have not been clear enough with my last post "Thirdly can you run up and down at an angle across the slope to reduce the angle your trying to get up." should have read as "Thirdly can you run up and down at an angle across the slope (ie. up to about 30 degrees from going straight up/down) to reduce the angle your trying to get up." I wasn't trying to say to run at 90 degrees to the slope, as yes could end up in all sorts of trouble. I have found by trial and error that I couldn't get up straight up the slope, but at a "slight" angle had no dramas.