2 pcs 1 mount

[The Oni]

Are there any rules for two combat-active characters being on the same mount? I'm not talking about fighting while riding double on a horse (because even if rules-legal it would be grossly impractical) but rather something like two Small characters on a Large or Huge mount, using special saddles or something, with the rear rider being a "gunner"-type ranged combatant.

Are there rules for it anywhere?

[Vendarien]

Check the mounts carry weight if the players and their gear fit within it I don't see it being a problem. A heavy war horse has a carry weight is 300 lbs. So 2 halflings could easily ride it. it has a medium weight of 600 so 2 humans with a reasonable load could ride but it would be reduced to 35 ft.

[torrasque666]

A heavy war horse has a carry weight is 300 lbs.

The very reason you don't see many Warforged Paladin's with Adamantine Body.

[jiriku]

Howdahs and sidecar saddles are described in the Arms and Equipment Guide, pp 78-79. It is a 3.0 resource. Making attacks while riding (not piloting) a mount isn't specifically addressed, but I'd interpret the book's silence on the subject as implying that attacks are made normally.