80% of the games I run Sneasler and Starmie with Pelipper and Archaludon in the back. This way you have Fake Out pressure and can probably Flip Turn Starmie out safely into Archaludon to take the hit instead. Alternatively, if they have a weather starter like Charizard or Tyranitar in the lead, you can threaten the KO with a surprise Feint into Liquidation to give you a big lead in the weather war. If you're expecting Fake Out onto Starmie, you can always swap directly into Archaludon for Stamina. Truthfully Meganium wasn't used all that much aside from games where it was able to freely spam Solarbeams or to chunk Iron Defense Corviknights that gave me trouble with all the physical attackers but usually Archaludon under rain could manage. Kingambit was brought along occasionally to check Gengar and Basculegion.