Oh hey, I can help with this! I own a few of the DZ B18 bodies and a DC Ada, so I was able to do a super quick headswap to show the fit/proportions/etc.
THE GOOD: The proportions and aesthetics are fantastic! I honestly like it a bit better than her default body, especially if you prefer a more mature look. Resin matching should also be easy since DZ and DC are sister companies, though DZ’s pink and yellow tend to be a little inconsistent and depending on how old the head is it might have yellowed/mellowed a bit.
The neck is too big, and so Ada’s head kinda just flops around on top of the neck and can’t really hold a pose. Also, the s-hook that comes with the B18 bodies is too big to even go through Ada’s neck opening, so you’ll have to get or make a really tiny s-hook; I had to use the one from my Ada’s body and then proceeded to lose one of the elastic loops down her body *ANGRY PTERODACTYL SCREECH*.
But with a bit of work I think it’d make an excellent hybrid! I’d say sanding Ada’s neck opening wider is a better idea than sanding the neck on the body, because the resin around the B18 body’s neck is already very thin and you don’t want to risk cracks or breaking. Even if you’ve never modded before this should actually be very easy, and sanding off 0.2cm shouldn’t take long at all! You should have it done in just a couple of hours if you’re doing it by hand with a craft knife and sandpaper, or just a few minutes if you have access to a rotary tool/Dremel. (Obviously all the warning for doll mods follow: respiratory mask and eye protection are mandatory, keep sanding work away from pets and other people, etc.)
Another thing I’ve experienced with all the B18 bodies is that they are very kicky right out of the box, so sueding is a must, and maybe restringing and wiring as well. I actually got the headswap girl to stand, though! Quite easily, in fact, I think the horns act as balancing weights. :o And once you get rid of the kickiness they are wonderfully flexible at posing.