While I've never played Superheavy Samurais, one of my friends does and I've faced against his deck a lot.
- Giant Rat: When it's destroyed by battle, it special summons an EARTH monster with 1500 or less ATK. Superheavy Samurai Big Benkei fits the bill. Since he switches to defense when special summoned, it's probably the most ideal way to summon him from the deck. Even if you've already drawn both of your Benkeis, Giant Rat still has another use. Every Superheavy Samurai has under 1500 ATK, so you can special summon any card in your deck when Giant Rat is destroyed. I would try playing two of them and figure out a balance from there.
- Superheavy Samurai Soulbeads: You can equip it to a Superheavy Samurai and prevent that monster's destruction once per turn. When a defense position monster is destroyed by battle and sent to your grave, you can discard it to special summon that monster in attack. This one might be more of a preference thing vs Soulfire Suit, but it might be worth running at least one for the revival effect.
Unfortunately, that's about all the advice that I have to offer, but I hope that it helped.
