You can move the pivots all you want, but the cylinder length is the same, and if you keep the same distance between the top and lower pin, you will still have the same degrees of range. What you gain in rollback angle, you will loose in dump angle, so just be aware of that.
If you move the pivots at the bucket closer together, you will get more range but loose some force, and will need to watch for clearance issues between the rod and the loader arm.
Also, most loaders have a mechanical stop, that prevents the bucket from dumping too far. Basically keeps the curl cylinder from bottoming out. If you change things, be sure to modify that stop, otherwise you can bust the front of the cylinder appart if you dump all the way and try to push something.
As to the welding on the rear axle, please elaborate? What and where on the rear axle. IT is likely cast, so not the easiest to weld on/to. And to to it right, the whole thing will need disassembled. Not only to preheat and prevent seals from being burned, but the oil inside will char and have burnt crispy's of oil floating around your hydraulics...not good.
