147px usable height from the top of the screen. That’s what I’m using as a guide based on what I see when looking at the OP-1.
Also, using a 8x8 grid for the 320x160 screen is helpful (obviously). Maybe a 8 8 16 8 px margin as a safe zone?
edit 2: Min stroke width and ratios is also something worth considering. And how the stroke is applied, center/inside/outside? More so for UI than for the art parts.