How to increase a constructs hit points?

[Corsair]

Wait, is it an actual warforged (which do in fact have constitution scores) or is it going to be a construct which is just an animated warforged body?

 

[enworldatemylogin]

Here is what I've worked up so far, in stat block format.

Medium construct
HD 3d10
Init +4
Spd 30 ft (20 in armor)
Armor class 17, touch 14, flat-footed 16
Base attack/Grapple +3/+7
Attack +8 masterwork morning star, 1d8+4
Space/Reach 5 ft by 5 ft
Special Qualities construct, dark vision
Saves Fort+3, Ref +5, Will +0
Abilities Str 18, Dex 18, Con -, Int -, Wis 8, Cha 8.
Skills None
Feats Improved Damage Reduction (fighter bonus feat), Spiked Body (fighter bonus feat)


Equipment
Final Messenger
Masterwork morning star
banded mail.

I would like to equip it better, but right now the gear above is the only stuff we haven't sold off yet. We had half plate +1 and a magic greatsword, but the party complained about needing the gold pieces.

As a construct, it gets no skills or feats. Having fighter levels reflected as HD, it gets 2 bonus feats. I've taken liberty with the bonus feat selection, but since it was described as having spikes when we first found it, that seems like a natural choice.

I was given 32 points for abilities, which means the higher than needed Wis and Cha. I guess it is relatively intimidating, (compared to my Cha of 7).

Considering we are all 6th level, I don't expect it to last long if pressed into heavy combat.

 

[Deadguy]

Just one small point: remember that constructs gain bonus hit points according to size (as d20Dwarf pointed out). So a Medium Construct gains +20 hit points for its size, making it HPs 3d10+20. That doesn't look quite so bad even if you just take average hit points.