Idk. I was watching Blastdowns tutorial and he said that 1x4x5 are the only ones that he can make and that a different size would require a different .blb file. And, as said before, I don't know a stuff about .blb files.
The only .blb file I made was the one for my safe.
The 1x4x5 file is default in the first JVS Door pack (1_4_15.blb), so it is easy to grab and use.
This reminds me that I need to update that tutorial sometime soon.