Hi,
I had to add a 3D eggplant to one of my games and noticed, that my AC3D license was too old and the uppgrade fee was raised a lot and whatnot. So I installed the new Blender 2.9 and after a few videos, I got the hang of it. It improved a LOT! If you want to do 3D, try this out.
So, the Blender export filter was broken due to API changes. I had a few nights to get that running again. The old script was about 10+ years old.

(reminder to myself: always comment code. Code you wrote 5 years ago is code someone else might have written...)
So, I fixed the export and found, the dda files were quite big. I inserted a scale factor for normals and vertex coordinates and now... the dda (ASCII!) file format is more compact than the ddd binary file format I used to be so proud of.
The trick is, that the vertex positions*1000 often result in numbers like "5" or "15", which is 2-3 bytes including a separating space caracter. The binary always takes 4 bytes per float. Same for the normal directions*100.
The next update will bring both, the export filter and the dda 2.0 support to you.