Another thing to note on the subject of using straight RTV:

The valve covers for the 3VZE are plastic with hard stops pressed into the screw areas. This is to avoid putting a compression load on the plastic, which is always a bad thing, as it will creep over time and you will lose your clamp load from the screws.

When you tighten the screws the plastic cover does not make contact with the head, there is a nominal gap designed in. If you do not use a gasket this gap would allow all of the RTV to squish out sideways.