3) With a new razor, X-Acto, or scalpel blade and remove a 1/32" (or less if possible) of the blade of the reed. You must have a clean square cut. Don't saw it off - press down quickly & cleanly. Once done though, you can't put it back.
You can also use a chisel. It's easier to "sight" straight across the edge and gently tap the handle down to cut of that sliver.

I have a Warnock and MacLellan poly that both usually have a consistent flat F. Pushing the reed in does help, but will sharpen the high hand more...hence more tape if needed. In my case, the D is already too sharp. Way too much tape...so, I tape the low A which helps the F and less tape on the D. I usually avoid ridge cut reeds and use molded reeds instead. Somewhat easier to manipulate. I use either Apps, McPhee, Abedour and Shepard (I use the Shepard reed in my ABW Shepard chanter).

The bottom line is that F is a pain. For me....one of the hardest notes to get right and I know of many "experts" that will say the same. Jim McGillivery's Pipes Ready DVD's has a segment on F and that it is a tough note to tune. He usually recommends to use various reeds until you find the one that works the best. This is trial by error kinda stuff....but necessary.

Remember to make sure the reed is warmed up before tuning. Going outside to play really does require you to tune outside and vice-versa. Also...this is important...do not tune drones and chanter near a fan of some sort. This will wreck havoc on the harmonics. Even computer PSU fans, ceiling fans, window, A/C, etc can directly affect how the drones are tuned which is in direct relation to tuning the chanter.