that seems a bit low though. that yields an AC of 19 for the Small, but 18 of the larger two. how about if we set the CRs, then do a bit of comparison?
let's see, they have the stun darts and vapor jets which are cool attacks, but the DCs aren't great. the crush is a very weak and specialized attack, and the power surge is a death throes attack, so neither of them should really figure into the CR. the flipping over vulnerability doesn't help them much, although they may not fall victim to it very often. they are constructs though, so they do get decent hp but sucky saves, plus a slew of immunities as well as the extra cold, fire, and electricity immunities.
they are definitely not as badass as golems, and are probably not a high challenge for the HD, but not total pushovers either. how about CR 2 for the small, CR 5 for the Medium, and CR 8 for the Large?