I'd be in favor of boosting AC, keeping them Large, but let them advance to Huge pretty quickly, like a wyvern.
Added to Homebrews.
Should they be hunting spiders, or give 'em webs as well?
Give 'em all the usual monstrous spider racial skill bonuses?
Do we want to boost the venom? Currently, it has the phase spider's venom as a placeholder.
Suggested level for rebuke/command? Equal to Hit Dice?
I like damage to multiple ability scores for this poison--Str and Con? I agree that these guys should get webs.