I think the problem are these files are wrong/not the full conversion.
The one the OP found seems to be just the normal U1 firmwares with the data part different only, thus your boot logo etc. would not change because it's the same one and not actually the sprint one.
We actually would need this one:
Links for each model are in the OP. Click on the link for U firmware, and that's what you'll get. Click on the link for U1 firmware, and that's what you'll get.