Hey Steve,
Apologies for the delay. For some reason I’m not getting notifications occasionally even for subscribed threads 
Give me a mail at info(AT)cubitstudios.com and lets see what I can do to help you.
Dithered AA probably won’t be a great alternative due to the visual artifacts but it’s worth a try perhaps… Unfortunately overdraw is one of those things that is hard to entirely minimize with particles sheets, and of course VR makes everything worse.