Advice on building a Master Blaster (and I don't mean Wizard)

[Echos Myron]

I'm talking a Halfling riding atop an Orc for a game of XCrawl!

The Rider, Gobbo, will be a Halfling, using THIS guide for the basis.

The Mount (and the main source of damage output) is Grull, an Orc (most likely) Barbarian.

We're playing at level 7, so a build will look something like this:

Gobbo
Halfling Order of the Dragon Inspiring Commander Cavalier 5, Battle Herald 2

Traits:
1. Helpful (Halfling Racial)
2. ?

Feats
1 EWP: Whip
1 Bonus Teamwork Feat: ???
3 Combat Reflexes
5 Bodyguard
7 Leadership

Grull
Orc Barbarian 5
1 Power Attack
3 Furious Focus
5 Extra Rage

My main tactic is to have whip & lance wielding Gobbo buff Grull with Aid Another.
What would be the most advantageous teamwork feat/trait in my situation?
What are some of the problems I fall into?

This is completely new territory for me so any advice would be welcome.

[Demiurge 1138]

I believe that you'll need Undersized Mount from ACG in order to make this work--bipeds can only be ridden if they're two size categories smaller.

[Cwethan]

Demiurge 1138 wrote:

I believe that you'll need Undersized Mount from ACG in order to make this work--bipeds can only be ridden if they're two size categories smaller.

Got a source on that, Demiurge? I feel like I see Medium characters riding Large Axebeaks pretty frequently.