Is a 9×7 tarp pitched in 1/2 Pyramid config. (holden) ok in rain?

It works for some. If there is wind you may get wet. I would only use a bivy with that setup in case of rain spray.

If you are sure of the prevailing wind and set the closed,  wedge end of the shelter pointing into the weather, it’ll work great. If the wind is consistent you’ll even have a dryish zone outside the open end.

Also tightly tie a short piece of absorbent string to the high end of the tarp’s attachment to the ridge line just inside the edge of the tarp. This is to wick and redirect the water traveling down the line, otherwise the water will  find its way further into your space before dripping or wicking down.

It occurred to me I could hang my rain jacket over the entryway, that seems like it might be helpful.

Skurka’s advice has been get a bigger tarp and skip the bivy, but that applies to A frame setups I believe. Sounds like I might be sorry w/o a bivy with this setup.

If you’ve followed the polycryo tarp threads here, you know I purposely design mine for the half mid pitch (it is closer to 9×6). If the wind shifts to the door direction, you may get wet if you can’t scoot back far enough. On my first tarp (LDPE one pictured in my avatar) I created a “storm door” for just that occurrence and it worked fine. I intended to make one for my current tarp, but haven’t yet.

@ the OP

Are you traveling below tree line?  If yes, then would you not have time to find sheltered areas to pitch the tarp?