He already knew exactly what he wanted, and went to select it. "Wait... It's combined into one option? Oh well!" He selected Womb/Testicle as where they'd stay within, but wanted to do an extra change here. He went back to the special instructions section, and started typing.
"When inside the host, most movements will provide sexual stimulation; Pedophilia laws entirely ignore this, as it's impossible to control. Coming to climax can force out any 'tenants', and during sex can result in them being left in someone else."
He went to confirm it, but thought about it. "Actually, could make this a bit more interesting..." He went back up and added an extra modification.
"If the host is female, she can still be impregnated regardless of anyone inside. Those inside may sometimes end up stuck for the pregnancy, but not always, with it being more likely as it goes on. During child birth, it's possible for the tenants to be pushed out before the child, or alongside; If not, however, they can also assist with the birth from the other side."
"In addition, it's possible, but often unwise, to go inside of the growing child. Entering the amniotic sac is one-way, and doing so will keep one inside for the rest of the pregnancy. Entering the fetus itself before gender is determined can result in unexpected results, and in rare cases even being trapped inside."
"In addition, impregnating a girl can be done while already inside the girl in question. Inside, age plays less of a part in these situations; Impregnating someone who hasn't gone through puberty can be done from inside, albeit far rarer, and only on purpose."
With one more thought, he decides to add, "If someone is an only child, they may stay inside of a younger friend until they get a sibling to properly stay inside, if both agree to this. This is not a requirement, however."
He decides that's about good enough, and hits confirm. The shift occurs, and his room begins to shift and become a storage room, only the Chronivac remaining. As it finishes up the change...