So here's a silly question. How do I change the window size in DOSBox, when playing in a window (obviously)? For reference, I'm using the SVN-Daum build. I've tried all sorts of different combinations of output methods (as I recall, 'Surface' doesn't like anything but the default window size), but I can't get it to do what I want. Additionally, in fullscreen, the game is shown in a teeny little screen (approximately the same size as the window), and the rest is blackness. I'd very much like to play this in the 'Super2xSai' scaler, rather than any of the 'HQ' or 'Normal' [number]x modes.

The window size is defined by the "windowresolution=" entry in the .conf file, so just set it to whatever window size you want. It doesn't have to be a normal resolution either. I'd recommend ddraw or opengl over surface (as you've discovered, surface doesn't support scaling outside of the filters).

As for the full screen thing, using ddraw or opengl as your output mode, set fullresolution to 0x0. That makes it run at your desktop resolution and it should scale up to that.
I don't quite understand the last part of your full screen problem. What's stopping you using Super2xSai?

Switching the output to directdraw works.

Slightly hurt that you gave the solution to the guy who said the same thing as me but later... =(

Because he included which lines to change in the .conf file.

I did include which line to change to set the resolution and you'd already tried different output methods so you obviously knew which line to change there.

Stop derailing the thread because your ego is bruised, or butthurt, or whatever the hell the expression is.

There's no longer a subject to derail the thread from, you've marked it as solved.

I think I'm entitled to be a bit hurt, no one had bothered to help you for ages when I came across the thread. I post the solution, someone comes along and reiterates what I said and you give that guy all the credit (someone who probably only saw the thread because I bumped it).

I posted the thread an hour before you posted a reply. I'd hardly call that 'ages'. Your solution was reiterated in a way that was simpler to read, an easier to understand. The point of marking a solution is to direct others to the most helpful answer. Furthermore, marking a solution does not open up the subject for freeform thinking, vis, your rant about not getting your extra e-peen points for providing a solution.

I don't care about points but it was rather disheartening to be ignored as I was. The thread has served its purpose though, the entire point was for you to get an answer to your question. Since you've marked one, there's nothing left to discuss (apart from this).