I don't play much Jason, but if you're talking about slasher, there aren't really any good reasons to cancel into shoulder charge. You have the low starting f42 string which is a launcher and the centerpiece of one of his main BnBs. (f42, f42, f42, f12 df1) To keep your opponent honest, you'd have to throw in some f2s (overhead) cancelled into df1 or ex df1. His fastest punish is the b122 string, which you'd follow up with an njp, f42, f12 df1 if it hits. You can also stagger that string for pressure. Pretty much all of his main strings launch, so really not much reason to cancel them into shoulder. If you want the ex shoulder brute, they have to be grounded anyhow. I find that f2 cancelled into ex shoulder works quite well, especially after a jump-in punch or a staggered b1/b12. But I can't think of any other reason why you'd want to cancel into shoulder over df1.