Hi Michael, the reason R5 on OSX won't import properly ... or i think it's the reason why, is when I import it opens a new session, so using your steps above is futile here;

Just to make sure i am not totally dumb, here's what I did

step1 ... Open the 3dm with R5
step2 ... Attempt to import OBJ file (R5 says sure, i will import that but here have a new workspace to play with)

However just for argument sake ...

step3 ... Select all cubes that are coloured black in new workspace created by the imported OBJ contents, select copy, and then paste those cuboids into the original session and the cuboids come in with their colours assigned correctly and are approx. 20% the size of the original cuboids in the 3DM file

Martin Spencer-Ford