1. The v-0.4 reduce the delay from 30" to 19"
2. In tree view the furniture completely disappear with plugin activated.
3. The perimeter are show like in image with no option to modify.
3.1 I suggest again to split in to different plugins and focus at this moment only on Grouper. After this one will be acceptable could concentrate to other one (perimeter or some more useful and complex).
4. I think is good to remove unnecessary dependencies and use as much You can from SweetHome (I don't know how, You're the programmer [:p] ) .
5. Don't forget the principle: Keep'it simple, keep'it free.