Joined: Nov 2016
It really depends on how the car feels when you have it out on the road (or track). Ideally, when you shift, it drops the RPMS down somewhere closer to peak torque, and rises right through peak HP. If you shift the instant you hit your HP peak, your engine goes back to doing a little less work per second. Shifting so your car is slightly past its HP peak may let the next gear hit at a spot where it's making enough power to be worthwhile. Other cars drop off in power really fast past the peak, and those cars would be better off shifting a little earlier.
This is an awesome question, but the reality of the answer depends on too many variables to get it right. You've got to deal with things like redline, valve float, how fast power falls off past the peak, and how slowly torque falls off past peak torque. You can sort of see some of the answers on that paper, but remember, you're dealing with shiny smooth dyno drums under your tires there - not dirty pavement (or sticky track).
Maybe the best way to think about it is this: If you had an infinite number of gears and could shift instantly, you'd want to ALWAYS have your car at peak HP for maximum acceleration. Since you have a finite number of gears, your best bet is to 'bracket' that peak so it falls in between your shifts, giving you the maximum 'average' horsepower within that RPM band before the next gear. Each gear will be different, because there are different drops in RPM involved.
ANY car will accelerate harder in a lower gear, so it's worthwhile to multiply torque as long as you can get away with it. The rest just depends on your engine and traction quirks.
The only way you will ever know for sure is to try it consistently each way a few times, and time it. You could also use a datalogger, if you have one. Or, do what most of us do, and use the Butt-O-Meter to guess at it. =)
I should add - with your car's super flat torque curve, I'm betting it will give you best performance running it up near redline before your shifts, but then again, you're sort of splitting hairs. Your car won't be too fussy about shifting a tiny bit earlier than its absolute peak performance, and the extra stress on your engine probably would not be worth it.