We done the same. mounting the target on a solid wood base 2 X 5" plank, also to get it a little up from the grass in the field, CUZ it grow like a SOB in the season.
The one we have we have experimented with angling it back and forth, but that have little effect on the FAC rifles overpowering the target and so just flip the paddle back or one of the other you have flipped flip back.
Also contemplated putting some rubber hose on reset bar, for a softer landing, noise not a issue at our place.
We have some other heavy duty spinners with a pig on the lower arm and a smaller bird on the upper, even short distance with a .22 air rifle we can not make those spin, they must be for a bigger caliber, it is also 6-8 mm thick steel.
So hitting those with a .177 even a 16 grain slug as 970 fps, it only make it wiggle a bit back and forth, dont even make it swing 45 degrees.
I dont even think amping my Two to the max and shooting 24 grain slugs will make it spin a full revolution.
These heavy spinners are also greased up, they are warm galvanized steel so as is they did not spin super well, but the grease gave little change.