Stage mode: 2 backgrounds in 1 stage, is it possible?

[YinYin]

I assume this is for a mod. If the background changes are limited to sub-stage changes, then it should be possible with hex editing (from what I remember). As in if you want different background for 1-1 and 1-2 then it should be fine. If you look back far enough, I think me and YinYin released something that did that (boss mode?).

That only worked upon directly entering either 1-1 or 1-2 from the menu. Moving on from 1-1 to 1-2 and changing the background didn't work.