new construct - bladed strider - please review

[Devon]

Bladed Strider (Huge construct)
Hit Dice: 8d10 (45 hp)
Initiative: +3 (Dex)
Speed: 60 ft.
AC: 18 (-2 size, +3 Dex, +7 natural)
Attacks: stomp +13 melee, bladestrike +13 melee
Damage: stomp 1d10+10, bladestrike 2d4+7
Face/Reach: 10 ft. by 10 ft./ 5 ft.
Special attacks: pin and strike
Special Qualities: construct
Saves: Fort +3, Ref +6, Will +6
Abilities: Str 24, Dex 16, Con --, Int --, Wis 16, Cha --
Climate/Terrain: any
Organization: solitary or platoon (7-14)
Challenge Rating: 4 (suggest 5)
Treasure: none
Alignment: always neutral
Advancement: 9 - 16 HD (Huge), 17 - 24 HD (Gargantuan)

Bladed striders are huge steel constructs built for use on the battlefield. These brass-lined clockwork machines are twenty feet tall, and have a pair of inverse legs attached to either end of a barrel-shaped body. Extending down from the body is a wide, flat piece of metal (like a wide ski) attached to a series of jointed armatures, as well as a row of long blades, also on armatures, resembling a wicked rake. It has a pair of gemstones facing forward which serve as eyes.

High atop the strider's body is a built-in seat wherein a humanoid rider can be secured for mounted combat; the strider can fold its legs beneath itself to let the rider ascend into the saddle. There are no manual controls, so the rider has to verbally direct the strider. A rider has 50% cover.

Combat:
The bladed strider is designed to pin opponents and disembowel them. The bladed strider can also stomp on opponents with one of its feet, or kneel to allow its rider to attack with a polearm.

Pin-and-strike (Ex): As a standard action, the bladed strider can attempt to pin and stab one or more opponents at least one size category smaller than itself. These opponents must be within five feet of each other and the bladed strider. The strider "steps" down on them with a wide metal plate, and then stabs with its multi-bladed sword armature. Victims must succeed at a Reflex save (DC 14), or be knocked prone by the plate, taking 2d4+7 damage from the blades.

Construction:
A bladed strider costs 80,000 gp to create. This cost includes the construct's physical body and all the materials and spell components that are consumed or become a permanent part of them. This cost includes 1,000 gp for the body.

Creating the body requires a successful Profession (engineering or clockwork) or Craft (sculpture) check (DC 14).

After the body is fashioned, the creature must be animated through an extended magical ritual that requires a week to complete. Understanding the ritual requires a 12th-level character with the Craft Wondrous Item feat.

Completing the ritual drains 1,200 XP from the creator and requires limited wish, polymorph any object, and geas/quest.

[Deranged Youth]

How do you make these? Me am likee

[Devon]

I made some changes to the original posting, and now the creation guidelines are accounted for. I removed the overly-complicated pin/gutstrike combo, making it a single ability.

Devon