Yo-SD, SDC, MSD, SD, SD10, SD13, SD16, and SD17 plus afew others are actually copyrighted by Volks, but because volks generally set the standards for BJDs, most people tend to use their terminology at this point. Volks and Customhouse are the oldest Asian Ball Jointed doll companies actually... However, this is kind of off topic on the vinyls. In the world of vinyls, there is only (for the most part) 1/6 "barbie," 1/4 minis, and the 1/3 50cm, 60cm, and 65cm.
Generally speaking, 1/6 is Tiny, 1/4 is Mini and 1/3 is Large. 50cm sometimes is placed in the mini category, but is generally considered to be a "Large." The 1/6 and 1/3 ends have the largest variety of sizes, but mini is only really the 40cm-47cm range for the most part minus a few of Bluefairy's and the Volks Ian (the first Volks MSD/a prototype) which are only 36-40cm or so (considered as short MSDs).
Dollmore, Supergem and Dream of doll clothing should fit DDs/DDDys.
List w/images of various Obitsu and Volks heads:
http://nijiura-doll.info/wiki.cgi?page=monsterFor the sake of bringing this up, is it Volks NORMAL skin that matches Obitsu WHITE skin or is it Obitsu NORMAL that matches? As I saw a matching hybrid with Volks normal + Obitsu white. Would be good to note.
Shows attaching a Resin Volks head on to an Obitsu body (may or may not be helpful?):
http://www.denofangels.com/forums/showt ... ost2709433Video of how to attach a resin head to a Dollfie Dream II body:
http://www.youtube.com/watch?v=cIVvSA_Ss7kThe only images I could find of an Obitsu vs a Dollfie Dream:
http://www.denofangels.com/forums/showt ... oll-nudity)&highlight=dollfie+dream
Clothing:
SDC, MSD and MDD are similar in size. However, SDC and MDD are a bit slimmer then MSD. I suspect the 50cm would fit in the slimmer "MSD" clothing, except things like pants and such would be short. Friends2Bmade would have cheap clothing that would fit, but it's getting harder to find (it was a part of Build a Bear). Just note SDC have smaller heads (6"-7"), while MSD is larger (7"-8") and I don't know what MDD is off hand.
SD10, SD13, DDII, DDDy are similar in size. The DD*s are slimmer however, but the clothing is mostly interchangable.
It's very dependent on the specific item in general.
Currently in Vinyls, there is only really a few sizes around right now.
Volks has: MDD (Mini Dollfie Dream), DD (Dollfie Dream, the originals which are actually strung with elastic), DDII (Dollfie Dream II, the current line) and DDDy (Dollfie Dream Dynamite, the really curvy ones)--no males, but has more head mold options
Obitsu has: 50cm girl, 60cm female, 60cm male, 65cm female and I heard rumors of a 65cm male coming out plus the VMFs which I don't know a lot about--larger variety of bodies
Back on the subject of body stockings, Volks has some, they're bust/legs covering only, which does work with more outfits, however unless your doll is "well endowed" they have a tendency to slide down. In my opinion, i would not buy one with a MDD as they don't tend to stay up well.
Ms. Geek bought some from here:
http://shop.ebay.com/beachgirlnikita/m. ... m270.l1313 Which are fairly nice, full body ones so if you want one, you could buy these or dare to make one. So far, they seem to be holding up pretty nicely.
With the Gretel head, I probably wouldn't go any larger then about a 18mm, as the 16mm already look fairly large and 18mm would probably totally fill up the eyes (Volk's Anime eyes are all 20mm or 22mm I think). However, you can buy some anime styled eyes in smaller sizes from Soul Doll called "bling eyes" link:
http://souldoll.com/shop/step0.php?b_co ... 0517072522 I do not know of any other companies who make these anime type eyes besides Soul Doll and Volks.
Also just to note, nothing larger then 16mm fits in the new Gretel's eye pockets (tried & failed). Soul Doll 16mm eyes will NOT fit due to their shape in the ones with eye pockets.
I would suggest considering getting a Den of Angels account (if you don't have one), at least for the purpose of going through the patterns and tutorials on the site, which there is a lot of if you're up for sewing.
Link to a tutorial on the site that shows how to make waist high stockings that I suspect could be used for a body stocking:
http://www.denofangels.com/forums/showt ... !-tutorialDDII vs DDDy:
http://www.denofangels.com/forums/showt ... ison-pics*Same link on Flickr:
http://www.flickr.com/photos/dollfiedre ... 883583445/Showing the inside of the DDII's joints:
http://www.denofangels.com/forums/showt ... n-Joints!!!
(sorry, HUGE post ^^;;;)