Nuvo Iron WPCP4B Black 4" x 4" Wood Post Plate Connector

what is the strength rating of these? I need to add 2 posts to railings on a 6' platform for a kids play structure.

is rhis made also for 6 x 6" nominal wood posts?

What are the outside dimensions?

Can I put wood skirting at the base of the post, will it sit flush??