TweakScale lets you change the size of a part. Not just that, but it will figure out how much fuel is in the resized part. And if it's an engine, it will become more powerful by scaling it bigger, or weaker by scaling it smaller.
Download: SpaceDock / Curse Source: Github
A bit of Documentation
Latest dev version (WIP stuff, might contain bees)
See also the development thread for the latest unreleased tinkering.
TweakScale was originally developed by Goodspeed and B
The drag mechanics are a bit hard to work around/with/change. When the part is -first- loaded (like..the very first time ever) the game engine will calculate the drag-cubes based upon the part geometry and planar projections. It then stores all of this information in the PartDatabase.cfg file (in the root KSP directory, next to the main game config file). Now, even if the model for that part changes (through recompiling the model, changing geometry, whatever); that initial drag-cube calculatio