OS are actually easier than you can think: to have an OS cancel you just need to put only one input direction after the special you want to cancel to.
I take the string 123 for example because it's easy to perform his OS select, in reality you don't want OS this string because it's unsafe.
Tools you need:
123
df3(forceball)
any direction input
Full input:
12, df3(forceball), direction(forward because in this case is easier, already done down-forward for the forceball).
Result:
12 into forceball, if not blocking;
regular 123 string if blocking.
I also tried "f3, forceball, forward" without adding any other inputs, it works, but the timing is more strict.
Result:
forceball if not blocking;
back to neutral stance after f3 if blocking.
Again try 123 OS to learn the mechanics, it seems to me hit advantage gives you an important info if a string/input is easily OS cancelable or not.
"12" has adv of +15f, and indeed you can easily do the OS fb.
"f3" has +7f adv, it's already strict to perform.
"f41" with OS df1(acid) after "f4" it's impossible for me; f4 has -2f adv.
