Trouble with Keys

I've really been wanting to find or make a Greek key pattern for weaving. It looks like it should be perfect for bar pickup, yeah? So I snagged an image of the design, scooched a grid over it, monkeyed with the sizes, marked it up, and got this: Doesn't look half bad in pixels, eh? Alas, this is what it looked like on the loom. Too narrow and too stretched out. I have GOT to get me a grid that's a different damn shape. Even knowing it doesn't work right, I keep thinking about it wrong. So I sat back down with the pattern, doubled the pattern width, and tried to work out how to fix the long floats. The problem with this pattern is... well, it's not how you chart a barred pickup. It works ok, but it doesn't show everything I have to drop in particular in order to get the right shape. But the way you do chart barred pickup doesn't show dropped threads at all, so I'm not sure what to do. It does come out looking pretty good, it's just a little mentally taxing to work on. It's in the 90s here, and with no AC, I am getting jack and shit done. Ugh. Getting this post written took me a week, and there's very little in it....