those don't look very stable to me.
if you pick something up, and get on an uneven surface to where one side of the rear of the tractor is not level wiht the other, the whole thing will go sliding off sideways.
A simple, easy solution to weld a plate to the bottom of the forks under the bucket. this will keep the forks parallel AND straight.
When welding, pay a LOT of attention to where the top plate welds to the spacer, and the spacer to teh fork steel. Pretty good tension loads right there, and if you welds are not VERY good, you will have problems.