Thats Ironic because that certain issue delayed a stage of mines that I was supposed to release, for about almost a week Lol
First off (theres an explanation)
Storage problems for stages is an EXTREMELY rare situation, for it happens by having TOO many textures, TOO many models, or too much data on a stage with limited Model Datas, because Model Datas are what extends the space, for example
If you have about 80 textures on a Final Destination based stage, and tons of big models, it will probably load but it would have very odd effects, or would just crash the game overall Lol
So this is solved by adding Model Datas, which allow more storage space and allow you to add more things to your stages
Im not sure the file size limit although I would have to guess probably around 8-10MB but that would be almost impossible for you would have to have TONS of Models and TONS of textures applying to MULTIPLE models in each Model Data of a stage like Big Blue or something, so thats not an issue
But if you ever have a storage space issue (again which is rare) then delete some unused textures, delete some unused models, or add more model datas (which is an upside because it would allow your stage to be compatible with more stages without the use of a .rel)