Has anyone used these rules with 6mm armies

I have used them, happy to answer any questions although should add I'm a solo gamer so might bend the rules as I see fit.

I'm planning to use them but unsure on how to base the figures.

I opted for the following as it allows me to use multiple rule sets (GDA 1& 2, Blucher, Polemos etc).

Infantry 16 figs 40x20 mm bases 

Cav 9 figs 40X40

Guns 1 or 2 guns 40X40

Command round bases

I use the Baccus bases as I find that they look impressive in mass

Infantry - 24 figs 60x30mm base

Cavalry - 9 figs 60x30mm base

Artillery - 1 cannon, 4 figs 30x30mm base

ADC's/Brigadiers - 1 fig 20x20mm (2p) round base

Command - 4 figs 30x30mm round base

GDA2 is excellent in 6mm. It's my favorite ruleset for Napleonics currently. I've played many rulesets over the years, and I'd say it's my favorite battalion level ruleset of all time.

Here's how I base:

Infantry: 3 bases 40X20mm, 54 figs per base

Cavalry: 3 bases 40x20mm, 24 figs per base

Artillery: 2 bases 40x20mm, 8 figs and 2 guns per base. Also 2 bases of limbers per battery

Command: 30mm base with 3 or 4 command

Brigadiers: 25mm base with 2 command

ADCs: 20mm base with 1 command

Here are some examples: