He may have measured the pin spacing, and he probably has that right, but the angle is all wrong.
Also, as mentioned above, the top of the bucket will buckle trying to transmit the force where it is mounted at now.
I would recommend putting the top pin hole just at the top of the loader mount, then the rear pin will be out away from the back some. The plates the pin holes are in will need to wrap a fair ways down the back of the bucket. Putting the holes down low will let the force be transmitted to the leading edge better, but you will need to notch the top rail for clearance at the boom so you can curl far enough to hold a good load.
Good luck, custom work is always a trade off.