I checked the dimension today and they will not work with a 4" dia. axel tube without modification. You would need to slot the u-bolt hole approximately 1/4" on each end. There is about 3/4" of material from the edge of the u-bolt hole to the edge of the block. So if you slot the hole you would be left with 1/2" of material from the bolt slot to the edge of the block.
In response to the question regarding shear strength; I never had any trouble with them and I did my share to abuse my rig, I have a pile of broken parts left in my wake...and this part is still like new. There were never any lateral stability issues that I could feel, the only sensation or feeling you get is that your suspension is not working so hard to flex.