Improved Familiar Riding Lizard caster level prereq?

[hisnamehere]

Just wondering where you might all put a riding lizard [FRCS 308] on the list of improved familiars?

I assume any familiar you can ride automatically bumps up the caster level requirements?

Riding lizard seems to be in between CL 5 and CL 7. Should I put it at CL 6?

Cheers.
Happy gaming!

[hisnamehere]

Any response would be appreciated. I gotta pin this down for a player.

Thanks.

[NoACWarrior]

If the familiar listed requires a certain cl and bab the its set in stone unless you the DM say differently. Using a monster in a novel way doesn't increase its CR rating thus making it harder to get as an improved familiar. At the same time you don't advance a familiar in the same way you do a monster.

[hisnamehere]

NoACWarrior: If the riding lizard was listed somewhere as a suitable familiar of such-and-such caster level, that would be great. Does it exist? Again, if not, any suggestions?

[Coidzor]

The Riding Lizard is basically comparable to a Heavy Horse, yes?