My Hennessey experience is that
in a "tropical" type of downpour, where the wind is minimal, the stock tarp works fine. As previously noted, there is not much room for anything else under the tarp.
I gave up with having the tarp attached to the suspension lunes. I could never get the tarp to pitch acceptably (yes, I know that as a flat tarp it will never pitch taught like a cat) so I started using a separate ridgeline. Much happier now!
The separate line allows you to attach the tarp BELOW the suspension lines, which results in the hammock being closer to the tarp and getting more protection in a rainstorm.
But for wind-blown rain, prepare to get wet with the stock tarp. The Hex is giant, and there are many other alternatives available.