The best part is no part.
I didn't say that - Elon Musk did... but he's got a good point.
In an effort to fly more and crash less - it's better to simplify.
IMHO, Linkage stoppers don't help with this.
Sure they're an easy out - and allow for simple rigging- but if they fail (and they've got more than one failure mode) - you're in a bind.
In a flying wing - you're basically down to deciding which direction to roll while enroute to the crash site.
That said - I'm a lazy man, and for ages I've been using linkage stoppers. At first I was more diligent about putting a thread locker on the parts involved - but like my gym routine - that too went away and was replaced with hot glue.
That worked fine for a while - well... until it doesn't.
Frustrated with another crash that was due to a failed linkage stopper - I finally caved and did about three minutes of math. Here's what I discovered: I'm an idiot.
Z bend pliers have been great for forming one end of my control rods... but why not the other?

With a little experimentation, and being certain to insert the control rod fully in the tool (flush with the tool's face when fully inserted prior to bend) I discovered it was simple to make consistent control rods of an exacting length.

For my tool, measuring center of servo horn to center of control horn (when flight controls are neutralized, and the servo is centered) gave me a fixed distance. (94mm in this case). My Z bend pliers need an additional 19.5mm of working material to make their bends. Call it 20mm because I went to public schools.
So if I cut control rods to 20mm longer than the on center distance (114mm in this case), and use my pliers consistently - I get control rods of the exact length I need.
Why this only took a dozen or so failures to figure out is a testament to my stubbornness.
I'm an idiot.