First, the containment protocols. The reason for the 7m x 7m locked cell is due to the compulsion effect the object creates.
Subjects within 3-5 meters of SCP-4510 experience an intense compulsion to directly view it, persisting up to 3 days. During this time, subjects may experience mild sleep disorders such as insomnia and sleepwalking, both of which increase in severity the closer the subject is to SCP-4510.
Due to the range of the compulsion effect, the cell would need to be in a different size than the 'standard', which I believe is 5m x 5m.
If an object has a kill radius of five meters, then it makes sense to have it stored in the center of a chamber at least ten meters to a side.
The quote above was from Dr. Mackenzie's Containment Protocols.
In my rewrite, however, the compulsion effect will be removed. A major theme in nearly all the critiques I have received regarding this draft is the outdated cliche of compulsion, therefore, it will be first thing I revise in the draft, the next being the then extraneous specifications for the containment cell.
Your point with the security personnel is definitely valid- the Foundation would probably devote security to more dangerous entities if the cell specifications are sufficient to prevent an escape. In fact, because SCP-4510 is not mentioned as having any weaknesses to physical weapons, security personnel are somewhat redundant in guarding it and probably serve as a downside, seeing as they could become vectors for the entity.
Subject will not display any psychological tendencies during Stage One.
Regarding your question on the quote above, the psychological tendencies are supposed to refer to the following effects in Stage Two.
Subject will show symptoms of insomnia and significant changes in sleeping habits, as well as increasing fear.
These effects, upon review, are in fact not psychological symptoms, so your point still stands.