In principle, you probably shouldn't be using it as much as usual. The Klaw is a vastly more attractive option in the ditto than in most other MUs for 3 reasons:
1. Bowser is huge
2. Bowser sucks at jumping
3. Bowser has a garbage spotdodge
These combine to make it difficult to dodge an incoming Klaw even if you're pretty sure it's coming. If you spotdodge incorrectly, you're going to eat a *hard* punish of some kind; including possibly a delayed Klaw. The correct answer to a read Klaw is to throw a hitbox out - with the opponent's positioning determining whether that should be a jab, ftilt, utilt, upb, or fair.
So, when you're in position to flame cancel, you're usually also in position to Klaw - so an intelligent opponent will likely be coming your way (EDIT: with a hitbox. I accidentally a whole phrase) shortly. Flame cancel loses to pretty much everything that Klaw loses to at the same range because the flame doesn't come out til you hit the floor. Therefore, you should be flame cancelling only when your opponent isn't likely to be at range to punish you at the time you land.
An exception to this is if you're against a cocky Bowser who is sure that he can read all your Klaws, and begins simply spotdodging them instead of more safely throwing out hitboxes. Flames punish the hell out of that.
Basically, flame cancelling is typically a very attractive option because it beats shielding AND spotdodging, but it's not that good in the ditto because shielding and spotdodging are both really bad in the MU. Use it as a mixup occasionally, especially at range, but be very cautious of overuse.
