The problem with noHitTimer is that it lasts a bit too long, which will make the block ignore some hits, for example:

Note how the block only gets hit every two jumps.
So in order to fix this, I want to propose this:
Set noHitTimer to 10 when the block gets hit
Set the speed of the block to 3.25 in the frames 1 to 4
Set the speed of the block to 3.25 in the frames 4 to 8
Set the speed of the block to 0 in the frame 9
This is how it would look with these values:

(It's a bit faster, more like SMAS)
I made an npc simulate this block-hit effect for test purposes:

