Wouldn’t this treatment of DCF bias cause issues on the Zpacks Plex Solo?

Guess much would depend on whether the canopy is .55 or .75.  Still, for a nonelastic material would expect reinforcement at the corners because that is where the force from the pullouts is greatest, as you indicated.  If they answer inquiries, you might let them know your concern and see what they have to say.

I see reinforcement on that corner. Whether it’s sufficient I don’t know.

Yeah there appears to be a circular patch at the corner.

That does have a main stress line (from the corner to the peak) that is running diagonally across the DCF (or “on the bias”). There is a patch at the corner but the stress runs in a straight line across the panel between the two fixed points (corner, peak) so the stress runs across a long unreinforced span where it is diagonal to the fibers.

Having stress running diagonally across DCF like this is the type of thing that does slowly deform and stretch apart the material (leading to eventual delam and pinholes). Most DCF shelter designs avoid this, but my guess is that it is present here as a trade off between weight and durability. The material is on a vulnerable orientation and not reinforced with DCF backed tape across the span, but that also is partly how they can get this so light.

So, for us Plex Solo users-to get as many miles out of it-don’t do a super taught pitch when not needed-little to no wind?

For a longer life I would add DCF backed tape across that span:
https://zpacks.com/products/54-tape-strip

It’s only about 2-3 grams and would look professional if you got the same color because it’s the same thing most tent companies would add here automatically. It’s important to reinforce the length of the span and not just the corner because the stress is present across the span so if you only reinforce up to a point then it’ll just move the failure point up to whereever you stop.

It’s all about how long you want the shelter to last. If the goal is just a few years or one thru hike then you can probably just leave it, but if you want it to last a long time I’d reinforce the span. Reducing tension is another option but you don’t really want to always have to pitch it a bit loose, and also the deformation isn’t so much gradually adding up, as it something that occurs more suddenly when you get into severe conditions. So pitching it loose but then tightening it up for storms isn’t going to help much unless you never get storms.

DCF canopy can last a really long time, but historically quite a few of the popular models haven’t been designed with that in mind which has created the widespread idea that DCF has a shorter lifespan. If a canopy is designed so that it doesn’t deform/delam there’s no reason you can’t get 300-500 nights like a woven tent.