HMS Upper Atack

BP: Jiraiya
AR: Circle Upper
WD: Circle Heavy
RC: Metal Flat Core (No Grip Flat Core )

I've been using it for a while and it's been working fine, but is there anything I'm missing? And a quick question, is the usage of Samurai Changer's CWD (Upper Mode) and Dark Leopard's AR legal?

I use something like this, but try the CWD from Sea Dragon.

And as far as the Dark Leopard AR question, I would assume so.

"Use in Smash Attack Customization

Special Smash Leopard + SCMS CWD Part custom
A deadly Smash customization can be created when combining Smash Leopard with Samurai Changer MS's CWD Part in Upper Mode. This custom has extremely high recoil and could potentially damage your Beyblade; so use this under your own discretion! To help with the recoil, using a grip tip is best to help it from self-KOing itself.

AR: Smash Leopard (Dark Leopard MS)
WD: CWD (Samurai Changer MS) Upper Mode
RC: Grip Flat Core (Dragoon MS) Or Grip Flat Core Ultimate Mode (Dragoon MS UV)"

this is taken from the wiki... it wouldnt be on there if it wasnt legal...

Yes that combo is legal, but like I wrote in the wiki article it is prone to destroying RC's.

As per your combo, I would really just stick with Metal Change core. It gives far superior control without much of a change in aggressive behavior

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Thanks to Kai-V for the avatar and signature!