is there a way to avoid Unity's auto conversion of textures to .psd?

Hello,

I'm working on an application to virtually dissect a 3D model of a human hand. It consists of about 100 different structures, all having their own diffuse/normal/specular map. For the best visual appearances, we've generated 2048x2048 texture maps for all those structures, which gives us a total of 300 (1x diffuse, 1x normal, 1x specular x 100) textures. Since Unity automatically converts those textures into .psd files, they get about 3MB each, so these textures alone will result in roughly 300x 3MB datasize, nearly 1GB. The textures theirselves are about 120kb each (we managed to reduce them in size without any detail/quality loss and still maintaining the 2048x2048 resolution), so the total package of all the 300 textures is "only" about 35MB as .jpg files...

Would there be an alternative way to work with these textures without the big data files they cause in Unity? (we've tried to scale them down to 1024x1024 and even 512x512, but the detail loss would be too big...)

Any imput would be welcome