Don't use a plan. Don't use a Cube. Don't make it a perfect Sphere.
Use a Center Planet Grave Well Block that pulls in all directions. Make it far larger then a normal block. Perhaps make this Planetary Grave Block start with a center normal size block surounded by a diamitor of 8, 16, 24 special Planitary Grav blocks. Let them be the only indistructible object ion the game or require special conditions to destroy.
This way, you can have your not so perfect (don't need to be any ways) spherical planet that branches out, block by block from the Grav well block diamitor core.
Use a Center Planet Grave Well Block that pulls in all directions. Make it far larger then a normal block. Perhaps make this Planetary Grave Block start with a center normal size block surounded by a diamitor of 8, 16, 24 special Planitary Grav blocks. Let them be the only indistructible object ion the game or require special conditions to destroy.
This way, you can have your not so perfect (don't need to be any ways) spherical planet that branches out, block by block from the Grav well block diamitor core.