Thinking about getting a tarp from Borah Gear, what extras should I get?

8 x 10 is massive for one. 9 x 9 would be better for solo use. Actually, an 8 x 8 would be ideal.

From Zpacks: 2 trekking pole caps and a package of Lineloc3's with loops attached.
From Lawson: bunch of Glowire

As far as size, an 8 x 10 is good for 2 people, palatial for one.
I would get some mid panel timeouts sewn on (2 each side).
I have linelocs on all of my tarps and shelters and I leave cords attached. When your fingers are frozen, it can be a pain untangling the lines but the convenience of the linelocs is a wonderful thing; so easy to get the sag out of wet silnylon shelters. They may save you from thinking you need a cuben tarp (it didn't with me).

I would get the 8×10. It is even minimally lighter than the 9×9. Also, 8' in width are plenty, but 10' in length can be very nice for bad weather. I can imagine that in bad weather, a tarp with 9' length might have to be pitched rather low, whereas a 10' tarp offers a nice extra foot of overhang over the head.
I used to have a 10×10 tarp and even with the foot-end pitched to the ground and the head-end at reasonable sitting height (120cm or so), I could crawl in enough so that no spray would reach my head. I don't even see the need for a bivy with an 8×10 tarp.

Actually, does anyone know the prices of their tarps?

Theo,

I can't remember the exact prices but I want to say the 9×9 and 8×10 were ~$100 and the 5×7 was in the neighborhood of $75 give or take a little.

I've yet to buy one of their products but they look like a really great deal. I had a chance to check out the Borahgami at the Pt. Reyes GGG and it also looked like a nice piece of gear.

To the OP's question… I prefer an A frame but I also have a stupid heavy 9×9 Kelty Noah's tarp that I hold on to for car camping. I've used the 9×9 as a diamond pitch over a hammock and as a lean-to.

Since I tend to use an Aframe more than any other pitch, the longer length appeals to me because during a storm, if the wind shifts and starts blowing rain in on either end, I have some options to shift one way or the other to move away from any spray.

How claustrophobic are you?

I lean towards the larger side as I like some headroom.

But larger can also take up more space, and sometimes that's at a premium.

Thanks for all the comments, really helpful! Everyone seems to lean towards the 8×10. I do plan to use this with 2 people one day, would the 8×10 be better for that?

Also for Katherine, wouldn't say I'm claustrophobic unless I feel trapped. I've never used a bivy or tarp before, but wanting to try.

I do like the fact I can cook under the tarp and won't be getting my bag wet from condensation like in my Tarp Tent Contrail.

I bought the 8×10 tarp over a year ago. The 8×10 and 9×9 were both the same price, about $95 IIRC, and nearly the same weight. It was spec'ed at 11.6oz on their page, as it is now, but out of the bag it weighed 13.1oz. There was a little shipping/thank you note that listed the actual weight.

Like others, I wanted the extra foot in length since I most often use an A-frame pitch. I don't miss the "versatility" of a square tarp, but then again, I've never needed that square symmetry for any pitches I regularly use.

Extras? I suppose that sometimes I wish I had a couple of ridge line or side panel tie outs, especially in snowy weather, but I do just fine without them. The biggest item I miss are linelocs on at least the main tie out points. I love linelocs, and at the moment I have them looped on that tarp with some cord. Not the most elegant or light solution.