Your ships as in:

• Ships you've modeled yourself. This is easy to do, simply scale down your model, or
• Default Sins of a Solar Empire ships. This is more of a pain that involves extracting the meshes into a 3d modelling program and then scaling them down before putting them back in game, unless there is a faster way a smart person (ie someone who's not me) knows of

I feel like your intended question is the latter in which case I hope someone can help you out.

Just remembered there was a mesh resize tool for Sins (Trinity version I believe), not sure if there is such a tool for Rebellion or not but certainly worth looking for as it would likely speed up what you're doing immensely.

Download http://www.moddb.com/mods/infinite-space

Install as mod

Start Sins

Activate mod

Profit

It would be far less work to make that mod 1.51 DLC compatible than go through the effort of resizing everything though.

Edit - I'm going to download it and see what files he's modded that might cause conflicts

Zom, if you can get it working (Or tell me how, I wouldn't mind learning), I'd really appreciate it.

-Edit: Fist, I'll give that a try if I have to do it from scratch. But what does that maxdiffusemiplevel line do? It'll be much easier for me to change it if I know what it does (peace of mind, and such.)