You mean the ones where there were multiple planets and moons and stuff? Last I heard there were collision problems in game. Thats the trouble with how the game reads planet mods. It doesn't read it has 2 seperate planets, but thinks the 2 planets are 1 big one. I had the same trouble so am adding some in as scenery.
A possible way aromd the collision thing is too drop the 2 planets way below in the minus y axis so maybe you could fly over the top of them. As long as you could still get close enough to use transporters. Not sure if this would work or if it would look any better then adding them as scenery. Since you wouldn't be able to circle them anyway.
I'd like to attempt it but its down about 25th on my to do list