Slow but steady the giant walks [PEACH]

[Obrysii]

I posted this a long time on another forum, but as it has found a new place in my new campaign, I'd like to get some more up-to-date feedback on it.

I realize that there is a Dire Tortoise in Sandstorm, but I have found its stats to be less than desired.

Dire Tortoise
Huge Animal
Hit Dice: 20d8+103 (183hp)
Initiative: +0
Speed: 20ft
AC: 28 (-2 size,+20 natural)
Attacks: Bite +16, 2 Stamps +11 Melee
Damage: Bite 3d6+15; 2 Stamps 2d6+7
Face/Reach: 10ft by 20ft/10ft
Special Attacks: --
Special Qualities: Retract, Susceptible to Diseases, Hardy Liver, Ageless
Saves: Fort +15, Ref +5, Will +6
Abilities: Str 40, Dex 10, Con 20, Int 2, Wis 11, Cha 8
Feats: Alertness, Blind-Fight, Endurance, Great Fortitude, Improved Bull Rush, Improved Overrun, Power Attack, Toughness
Advancement: 21-25 (Huge); 26-30 (Gargantuan)
CR: 10?

Dire Tortoises are much like their smaller cousins: heavy, thickly armored, and slow. They look just like them, except they are about the size of an elephant.

Retract (Ex): A Dire Tortoise may as a standard action retract fully into it’s hard, heavy shell. This effectively drops it’s dexterity to zero (thereby reducing it’s AC by -5), but it gains Hardness 8, as it’s shell is thick and strong. It may take no other actions except to return to its normal forum, which is a standard action.

Susceptible to Diseases (Ex): A Dire Tortoise, as is it’s smaller cousin, lacks as powerful immune system as a normal animal, and as such they are more susceptible to diseases than an ordinary animal. They take a -4 penalty to saves against diseases.

Hardy Liver (Ex): A Dire Tortoise consists mostly on plants that a normal animal would consider toxic, and as such have developed a resistance to most poisons, since their livers are able to metabolize them more readily. Dire Tortoises have a +4 racial bonus to fort saves against poisons.

Ageless (Ex): Dire Tortoises do not die of age, though their populations remain in check due to hunting and their weaker immune system.

Training a Dire Tortoise
A Dire Tortoise may be raised as a mount, though it requires a successful handle animal check (DC 30 for young). Young are worth 6,000 gold. A trainer charges 2,000 gold to train one, and riding one requires an exotic saddle. A platform may be attached to the shell of the Dire Tortoise.

Carrying Capacity: A Dire Tortoise can carry up to 12,768 pounds as a light load, 25,536 pounds as a medium load, and up to 38,400 pounds for a heavy load. A Dire Tortoise can drag up to 192,000 pounds.

New Item:
Platform: A platform is a large board, usually made of wood, about 10ft. by 10ft in size, that can be attached to semi flat objects (such as the shell of a Dire Tortoise) to provide a more useful, flat surface for carrying things. Anything that can fit into said area, and is lower then the mount’s maximum load, can be put onto the platform and used (such as a ballista). Price: 400 gold.

[Shades of Gray]

I so want one of these as an animal companion

[Obrysii]

So, is this pretty solid mechanically?