>>9667921As for size, 16-20mm diameter has been ok for me, but most important is the iris size imo. I 3d print my eye bases, and they have been even a bit too big (22mm iirc) for the those particular eye models to look ok. So many RH customs have too small irises and they look psychotic in my opinion kek. I also bought some eye base molds from Aliexpress and they were kind of small, at least the iris was. Of course you can always paint over the "cup" to make the iris bigger.
Are you planning to buy eyes or make them yourself? I think there are quite a few tutorials of making them on Youtube / doll blogs etc, lmk so I can help more! As I said I use printed bases, then paint them and use UV resin and a UV flashlight / torch to harden the resin in small layers, adding glitter between some. My first attempts were with printer resin, but I think it's so much more reactive with UV light so it went apeshit and became super uneven?? Normal jewelry etc craft UV resin is much better.
BJD eyes usually get attached with a blue tack blob or similar to allow movement when desired, but the fit was not that good for my eyes so I just kind of forced them on there with super glue and activator spray. That stuff is godsend! You can find it in hardware stores for really cheap, it makes the super glue super strong. I use it to close the head back up as well. Sometimes (or eh, most of the time if you are me...) you get a bit of super glue on the eye itself, it's fine. If it's thick enough to become white, scrape and / or sand it off. Glazing the eye with varnish or resin will make it shiny again. I also attach lashes with resin on top of the eyes, but pva glue works too (and is easier to remove in the future if needed).
Whew ok, maybe that was most of what you asked? Feel free to ask more if you need to! Hopefully you are still here.
Picrel is my newest custom Poppy! The faceup itself turned out nice I think, the eyebrows are a bit derpy maybe.