I need to increase the size of the field you make models in by at least 20. It really doesn't make sense why you cannot go beyond 126x126x126 because in the MagicaVoxel viewer, there are sample models of 1000x1000 so there's gotta be a way to make larger models in MagicaVoxel. Anyone know how?
You can't, really. 126x126x126 is MV's limit. You can combine two scenes together using MV_Import and MagicaVoxel Viewer, but SLAB6 supports 256x256x255, and Paint 3D can support all the way up to 1024x1024x512. I highly recommend you check out the tutorial I linked if you want to keep using MagicaVoxel (I mean, it's free, so why the heck not), but SLAB6 and Paint 3D are your best bets if you feel like switching tools.