I'd be glad to help. DQ and DQ2 seem like ideal games for the SP4. Just let me know what you need. After this week, I'll be back at work and could only test evenings/weekends.
For what it's worth, the art scales perfectly and beautifully, but the text is a bit pixellated and aliased.
That being said, I think the cutscene sprite placement may be slightly off. In the caravan scene with Azra's arms spread, her right hand is off to the side of the screen and into the black area. Just tested the demo on my desktop (1920x1200) and she's placed well within the background.
I've also noticed that on the SP4, the wave indicator is on the top, while on my desktop, it's on the left side of the screen. Overall, I'm impressed with how you've accomodated the scaling to different displays. My 3:2 and 16:10 displays aren't the most common, and the game works well on both.