SFP, I've mentioned this in the IRC, but if you think I'm talking about just running away and spamming special attacks, you've got another think coming. Yes, Paralyzer and Plasma Whip will be helpful on that stage, but they're more to keep DK honest so he can't approach with bair, which basically means he can't approach. This leaves you to get an early lead with suit pieces and wait for DK to try another doomed approach. Trust me, I've played Ragnar0k several times in tournament, and he has never beaten me on FD. It's that bad for DK.
You don't get it. Any time you gain the advantageous position on this stage (directly underneath the platform), DK just goes off the stage and forces you out of your advantageous position with his invincible UpB. Any time you hit DK, he can just put things back in his favor by washing, rinsing and repeating. There is no advantageous position for you on this stage. Your best bet here is to ledge camp, and even that is barely an even match-up.