glad it helped! and thanks for the well wishes - i'm doing better today after some much needed rest.
calculating the pixel coords was confusing to me at first too. i didn't initially realize that pulp doubled the size of the pixels - so instead of the native 400x240 we have an effective logical resolution of 200x120. that's 8 logical pixels per logical tile (not the 16 physical pixels you might be trying to use like I did?)
EDIT: for clarification, it's 8 pixels per axis. e.g. the X axis is 400 physical pixels, 200 logical pixels in Pulp, or 25 tiles. the Y axis is 240 physical pixels, 120 logical pixels, or 15 tiles. so there are actually 16x16 physical pixels in a tile (=256) and 8x8 logical pixels in the same tile (=64).
also as a word of caution: using fill with negative width/height changes behavior. i'm still trying to figure out whether it is a bug or a feature... i'll make sure to update my post once i know that answer: Persistent Fill with negative W,H?