Tales of Known Space

[DavidG]

I've been wondering if it would be possible to mod the universe to bring in the concept of Pupeteer Hulls. (ie really tough but only made by one race and traded to the others) The invulnerability thing I get (although probably don't really want them totally invulnerable) but I'm wondering if it is poossible to have only one race be allowed to build them and then another could trade for them and upgrade it with components. I'm thinking this would be impossible since I think you would have to be able to build a hull before you can upgrade it.