I didnt understand how important UVing was until I got on a team that develope a game that comes on Steam. UVing is the most important task in modeling and texturing.
You can still paint it in Substance Painter for sure. Just remember that, whatever&wherever you put down in 0-1 space, it will be repeated to other 3 quadrants at the exact same spot.
Here's an easy way to fix it. If you laid out your shells outside the 0 to 1 space, into 0 to -1, -1 to 1, etc. Here's an easy way to remedy it: Here's your shells outside the 0 to 1 Select them and move your scale pivot up to 1, 1. Like so: Then scale your shells in both U and V directions until they fit nicely into the 0…
I use Maya 2014 to unwrap. The only plugin I use, for UV mapping, is Nightshade's UV Editor. Its has some amazing tools that I couldn't live without. Once you get a good workflow down, there's nothing wrong with Maya's UV tools..