DUB
Smash Lord
So? You're going to fall for getting bair'd while you're stationary and he's in the air? You can just throw a naner at him and then pluck another out.
I'm going by the original post you made about DK on japes. yeah you can hit him with a naner while he's bairing but to think you can camp on the smaller platforms the entire match like this is ridiculous. I have outrageous amounts of experience with this matchup against one of the best DK's on the east coast. The two small platforms are no place for Diddy in this match. Popgun ( which I agree is very effective) is not going to stop him from getting on there with you. When he does get to you shield grabbing is definitely an option. DK has great mobility options on this stage and to think he can't quickly get to the edge and use any of his stunning get-up options from there on you isn't too bright. If you are that close to the side of the stage anyways and you do manage to get hit you are dead at a very low percentage. I've done the exact same situation you are talking about and it turns out different every time. He can Air Dodge to you, get to the ledge and go from there, AD the banana and bair through your popgun ( if you shield the bair you will be pushed back to the edge, making out for a very ineffective camp. Hell, he can even just Donkey Punch through your banana with his SAF and then you are definitely dead. Even an average DK will not allow you to camp him on Japes.
I don't think Japes is necessarily bad for Diddy against DK, but the matchup itself is completely centered around caution.