I increased the planet sizes to double.  The surface area should be double and also there may be a lot more items generated on the surface of the planets. Give it a try. It's not glitch free. Graphics can look ugly during atmospheric entry, since the game only renders a small portion of the planet's surface for higher level of detail.  It should look fine, once you are close enough to the surface.

Note: It may be not completely finished, so I'll update as I edit the files.  

User experience may wary 

Unzip the .pak file, place it into your /No Man's Sky/GAMEDATA/PCBANKS  subfolder.  

Uninstallation is delete the _MOD.Planetsize.pak from that directory.