Trouble with object placement. Any suggestions?

[Zepper]

I don't know about any other NES game that uses multiple scrolling though... Most of them uses up and down like SMB3, or vertical rolling like Darkwing Duck, TaleSpin, Metroid and much more.

You should use some trick to get the effect you want. Of course, give a look into blargg's multi-threading demos to build some efficient work.

[tokumaru]

Most of them uses up and down like SMB3

That's multiple enough, no? There is no way to scroll more than both vertically and horizontally at the same time. Except if you are coding something 3D. Some games though, like SMB3 or Kirby, restrict the height of the level.

or vertical rolling like Darkwing Duck, TaleSpin, Metroid and much more.

That's the simplest kind, as you don't have to worry about complex attribute table operations, comples column and row rendering, complex object placement, etc.

You should use some trick to get the effect you want. Of course, give a look into blargg's multi-threading demos to build some efficient work.

I have all the scrolling engine figured out, and most pieces of it coded already. I have just to code the logic that will glue it all. And I also know how many things will be done, I just haven't yet. It's not like I'm just starting the project now.