I'll take a look at it tonight. This dial-up connection isn't exactly YouTube-friendly...
Anyway, I don't think glitching through the locked door to the second floor would do any good as I'm sure you'd end up in a blank room similar to the one behind the front door of the castle that you can get to if you were to run through a certain wall.
In other words, the spiral staircase has it's own screen as opposed to, say, the rooms for Bob-omb Battlefield, Whomp's Fortess, etc...