I have started adding zerks to my balljoint upgrades of the standard A-arms. The 6mm zerks can also tend to slightly spread the gap of the Black bushings with outward pressure... So to install, I add the 2 black bushings first and pinch with a C-clamp, and then drill and tap for the zerks. That clears the way nicely.
For DIY to stock A-Arms, I'll be putting together some zerk kits with new black bushings, and will include 8 pcs of bonded seals to seat and boost the zerks, along with a drill bit and tap as optional. I've seen those Moto zerk spacers ooze under gun pressure, so a bonded seal may be better and does the same job. I have 2 types of bonded seals, and both are cheap...cheapest version shown in the pic. I agree that every stock A-arm set will benefit. If you need some misc pcs, just give a yell.