This will be the storehouse for information regarding STEP and Skyrim:Special Edition (SSE).

Optimize extracted textures with Cathedral Asset Optimizer. If you have LE with HD pack: Extract all the texture BSAs with Bethesda Archive Extractor. Games: Skyrim, Fallout 3 & NV, Stalker, Oblivion, Morrowind, Mount & Blade, GTA4 and others. Textures Check, Fix, Compress, Improves Perfomace.

Make your body AND your hands and feet in BodySlide. And changing the chest size in BodySlide has nothing to do with the hands either. If you have a gap between the body and hands, editing the texture will do nothing. The two - textures & meshes - have nothing to do with one another.