I floor tiller with my tips left square at say 5/8", or so. That way I don't worry about flexing and grinding them into a piece of carpet as I floor tiller. In order for me to use a tree as early you do/did, I'd have to somehow shape those tips down in a way I can get a string on them. I don't want to do that so early in my process. So, I floor tiller to about 10-15# heavy, add overlays and/or mostly shape the tips and add grooves, Then brace it low and tweak it from there.