Ok this is what I have experienced on kato decals. This was on the main side of loco.  They suck to remove. Tried the microsol, tried the 91% alchohol, (Lots of patience). Ended up after all of the processing ... used an xacto knife....and carefuly removed the 6 (Rd.# 7216)... Then Tried to add the 0 to make it Rd. # 7210. (I was successful)  Note... I planned on the 0 but it just happened to work out to cover the 6
Main shell was not that much of a problem with xacto knife. So I am done but hope not to do this again
Now to the fun part.   The number boards.... I had 12 decales.. (# 0) By the time i finished with this one loco.... I have (0)  left...
Here is what happened...  Some that wouldn't stick, some that would tear, and some that tore on place after I was done and thought all was well.. 
I went back to find out that one had mysteriously jumped off and landed on my bench?  
Overall I am happy with the outcome but I wish manufactures would let us apply our own rd.#