The spell Stone spiders bed:
You turn 1d3 pebbles into stone constructions that look like
monstrous spiders. Buildings can be of any size, from tiny to huge,
you decide, but all the builds you create must be the same size.
Buildings have the same stats as monstrous spiders (see
Annex 2 of the Monster Manual) of the appropriate size, except in cases
follows: Their natural armor increases by +6.
They have 30 / + 2 damage reduction.
Their poison has a Fortitude save of 17 and your Wisdom modifier.
Initial and secondary damage is 1d3 points of temporary Strength damage. (FRCS, 75)
It seems simple enough. But the MM (page 307) says about constructions:
Features: A construction has the following characteristics
– Dice Hit with 10 faces
– Basic attack bonus ewual to 3/4 Hit Dice (as cleric)
– No good backup jets (…)
– No constitution score.
– vision in low light.
– Darkvision at 60 feet.
– Immunity to all effects affecting the mind (charms, compulsions, fantasies, patterns and effects on morale)
– Immunity to poisoning, sleep disorders, paralysis, dizziness, effects of illness, death and necromancy. (…)
– Not subject to critical hits, non-lethal damage, capacity damage, loss of ability, fatigue, exhaustion or loss of energy.
– Immunity to any effect requiring a backup of Fortitude (unless the effect also works on objects or if it is harmless).
– No risk of death due to significant damage (…). Immediately destroyed when it is reduced to 0 hp. (…)
The MM also assigns the HP bonus to size-based builds.
If you apply all these traits and features to the monstrous spider, you get a creature that has almost no "the same stats" as the monstrous spider.
A huge "stone spider" would look like this:
Init +3 (+3 dex)
AC 22 FF 19 Touch 11 (-2 size, +3 Dex , +11 natural)
HP: 84 (8d10+40)
Fort +2 (immunity to all effects unless effecting objects) Ref +5 Will +2 (immunity to all mind-effecting effects)
Speed 30 ft. (6 squares), climb 20 ft.
Base Atk +6 Grp +18
Attack: Bite +8 2d6+6 plus poison DC 23 (1d3 Str/1d3Str)
Full Attack: Bite +8 2d6+6
Space 15 ft. (3 squares) Reach 10 ft. (2 squares)
Abilities Str 19(+4) Dex 17(+3) Con -- (+0) Int -- Wis 10(+0) Cha 2(-4)
Darkvision(Ex): 60 ft.
tremorsense(Ex): 60 ft.
Low light vision
Immunity to all mind-effecting effects, poison, sleep, paralysis, death, stunning, disease, necromancy, critical hits, non-lethal damage, ability damage, ability drain, fatigue, exhaustion, energy drain all effects that require a Fort save (unless effecting objects).
On the other hand: if you take the spell to the letter, you will get a build with a Constitution score, which is very strange.
So, my question: do you really go with the Monstrous Spider stats or do you apply any construction traits to Monstrous Spider (with the exception of the DR which is explicitly defined in the spell)?