Doing it on Halberds lip is REALLY useful because it makes us one of the only characters who can get out of it semi-reliably with no double jump and it looks cool af.
I thought you generally don't have enough momentum from the rebound so that your 2nd PKT doesn't hit the underside of the stage, also I'd like clarification if it works on the left walls or do we just ricochet off and die?
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Anyway, I say Delfino IS Ness' best stage, BUT I would prefer to avoid it OR you have to watch out for a gimmick against the following characters:
- Jiggs can get free Rests in the water with no penalty as she instantly wakes up when she touches the water. Same can apply for Kirby's Stone AND he might be able to get U-Throw KOs there earlier with the platforms as the camera zooms in and the ceiling gets insanely low. I might be able to say the same thing against Charizard and his Rock Smash and U-Throw as well lol.
- I love the Fox MU and Delfino, but it's not somewhere I'd CP against Fox since we have the upper hand against him with edgeguarding, and I feel Delfino takes away that aspect. Also, one of the things we love about Delfino is that Ness' recovery isn't much of an issue there, BUT Fox really can't threaten Ness' recovery without the risk of SDing in the first place.
- IIRC DK and Ike have some good things for them over there, esp. with their spikes in the water and it helps with their recovery issues too.
- I would also avoid taking Yoshi there, I mean Yoshi does well all around on any stage but I'm NOT comfortable there against Yoshi tbh.
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Now, regarding the benefits for Ness:
+ In the sections where there is a lowest platform or we're protected by a wall of some sort (say the section with the parasols, the bridge where there's a pool at the left, and the Shine Gate), I like to go to the lowest level, hide by a wall and try to force approaches with PKT and Nair them if they come to my zone lol. It's also useful against those with projectiles that you can absorb, since if they come toward you with a projectile, you can just jump out and Magnet.
+ Walk-offs help us get earlier KOs with B-Throw/F-Throw/D-Smash/Nair/Bair, also you might be able to Fair chain someone to their death. XD
+ We are usually worry-free about recovery in most sections.
+ The section with the grassy stone pillars lets us just Nair opponents that get caught in between them for days, also lets us play some nice ledge PKT tricks (let go, double jump PKT, grab ledge, then move to the pillar next to you where the opponent isn't and send PKT their way, 2nd time you regrab ledge you're on a new platform so you're usually safe lol).
There might be more that I can't think of atm but Delfino is usually my go to CP! :D