There is a way to change the resolution in-game by pressing "R", and it looks like there are 2 options, but is there a way to make the default res the high resolution? Every time I start the game, I have to manually change it. Is there a dosbox setting that will do this?

Thanks in advance.

This is a game function, not a dosbox one. Unless there are command line startup parameters for this game that I'm not aware of I really don't think there is a way to change the default setting. Given how 640x480 has a tendency towards minor graphical glitches, especially near the edges of the screen, I think the game was made with 320x240 in mind.