It seems the game does another check before launch on weight. Freezing the value doesn't help. Let me know if you have any luck getting the game to launch with an altered weight.
It used to work just fine...you would locate the values for weight and cost, and once you finished building your ship, you changed the values in the mem editor and then clicked on one of the modules (like say aux engine) and then clicked off without selecting anything (it would reload the correct values if you made ANY changes, even if that change was just selecting the module already mounted again). The new patch seems to have broken it somehow, I havent been able to get it to work how it did before. I'm going to play around with it a bit and see if i cant figure out a way to make it work again.