Freaky! Congratulations on a fine build , won't find many people Midwest USA that would even try such a feat! We need you over here! Lol well trade ya some of our worthless citizens .
I converted a Bobcat backhoe from skidsteer to 3pt attach, and it will pull my 3011 skidding sideways when prying on concrete... Even though its only a toy compared to your backhoe. So, you bet it will move when you tear up stumps or rock...It stays in position when digging soil, but I expect some movement once I try to dig out a stump