Creating a sideboard plan for a Red-Green Vehicles deck in Pioneer can be influenced by the metagame and the specific matchups you expect to face. You can reference them from the recent MTG tournament results posted on various websites. However, do remember to adjust your sideboard based on the meta at your local game store or tournament.

Here’s a starting point for your sideboard in the Red-Green Vehicles against the common metagame decks in the format:

Against Aggro Decks (e.g., Mono-Red Aggro, Humans):

• 2x Aethersphere Harvester: Provides lifelink and can block well against aggressive decks. The Chariot can already gum up the board early on if your elf lives to tap for extra mana. 
• 2x Abrade: Deals with small creatures and can destroy artifacts, which can be useful in certain matchups.
• 2x Obliterating Bolt: Effective removal for creatures with toughness 4 or less and can exile them. 
• 1x Scavenging Ooze: Helps gain life and remove creatures from your opponent’s graveyard.

Against Control Decks (e.g., Azorius Control):

• 2x Cindervines: Puts pressure on control decks by punishing them for casting noncreature spells.
• 2x Pithing Needle: Shuts down problematic planeswalkers or other key activated abilities.
• 2x Reckoner Bankbuster: Provides gas with card draws and an added 4/4 board threat afterward. 
• 1x Chandra, Torch of Defiance: Generates card advantage and can deal damage to your opponent. 
• Hazoret the Fervent. An indestructible God creature that can be efficient in the late game and can make any card drawn deal damage to opponents. 

Against Midrange/Grindy Decks (e.g., Angels, Bring to Light Decks):

• 2x Chandra, Pyromaster: Generates card advantage and can help deal with opposing creatures.
• 2x Roiling Vortex: Puts pressure on your opponent’s life total and prevents life gain.
• 1x Chandra, Torch of Defiance: Additional card advantage and threat on the board.
• 1x Shapers’ Sanctuary: Helps protect your creatures from removal and generates card advantage.

Flex Slots (Adjust Based on Your Meta):

• 1x Aethersphere Harvester: For additional lifegain and flying threat.
• 2x Rending Volley: Deals with problematic blue or white creatures such as in Humans and Spirits matchups, and planeswalkers of those colors. 
• 1x Thrashing Brontodon: Provides artifact/enchantment removal and a decent body that can attack.
• 1x Domri, Anarch of Bolas: Generates card advantage and can give your creatures more power.
• 1x Chandra, Torch of Defiance: An additional copy for control matchups or grindy games.

Remember that your sideboard should be tailored to your local metagame and your play style. Be prepared to adjust your sideboard based on the decks you encounter most frequently.

Additionally, always keep an eye on the evolving Pioneer metagame for new cards and strategies that may impact your sideboard choices, especially now that Wilds of Eldraine is now legal to play in the format.

Thanks for reading and until the next blog post.