how Do i get everything onto one UV map?

I'm currently UV mapping and texturing my mods! which is more complex than I thought, Uv mapping is not fun especially for complex models, but once I learn everything it will be easy!

Problem 1. (Fit everything onto one UV map?) Currently I have UV-unwrapped the roof and the floor of my vehicle onto the same UV map. I want to UV map most of the body of the vehicle to that same UV map but I am running out of room, Is there a way to add more room to the map area? or do I just scale down the existing UV maps to fit more? <--but wouldn't that downgrade the visual quality because of being sca

Problem 2. (Smaller size files) Currently Im baking the UV normals at 8196x8196 (for better quality) so the file is huge (a few MB's, to much for smooth gaming, I notice that the official vehicles have very nice maps and I think they work on 4096x4096 and the resulting file is small (i think a few kilobytes) <-- how do they do it? Do I need to scale down the .png file? will that mess up the location of the UV maps on the vehicle because of being scaled? I can scale it down in Photoshop and preserve the quality.

 

Problem 1:
You can try scaling down the unwrapped parts, so instead of having the roof and floor take up 100% of the image, make it take 25% so you have space for the other parts. Might not be the best to do but it should work somehow.

 

ok thanks I will try this!