leaf spring lift block question

[Jc12]

Hey guys, i am installing some block spacers on my little farm trailer and am new to this. I am wondering as my pieces of steel are slightly wider than the ubolt width (ubolts are 1.75" and blocks are about 2") am i amble to cut out little notches (kind of like a tunnel) for the legs of the ubolts to run along the block? Is there any reason this is a bad idea? Do the ubolts shift at all on the axle? Thanks

Here is a pathetic drawing of what i mean if you were viewing the lift block from above.

 

[fourwd1]

Since the blocks are steel you should be able to get away with it, especially if its a light duty trailer.
But the big question is WHY ???