I had a bad second day of sailing at a regatta in light air.  The helmsman was trying too hard to point, we lost boat speed and we fell way back.  I started playing with Excel and looking at footing.  The data has been amazing.  My take from my data is that it is better to foot than it is to loose boat speed in light air when you are closer than 45 degrees to the weather mark.  My data agrees with what Mike is saying.  I stumbled upon this when looking for strategies for footing.  I am almost done with my excel worksheet.  I have about 6 variables.  My boat speed is in boat lengths and I am using a percentage cooeficient to adjust speed when footing or pinching.  Footing can equal 1.05 boat lengths.  Pinching can equal 0.95 boat lengths.   Or any amount I choose. Its all make believe but the results are all the same.  Each column is a boat.  So I can add as many boats as I want and compare how close the boats are at the weather mark.

Super cool concept! But you need to correct the route drawn on your slides, for the starboard tack! You will not foot anymore after tacking!

- this tactics work because it makes you reach layline faster. Not the current layline, but the one corresponding to the wind AFTER the shift.
- BUT after tacking, you need to sail at VMG for that tack. So it will be the same angle and route as the other boat sailing the laylines normally, but just coming from further back on that layline

It just makes you reach the future layline faster

This is sound on paper but you need to take into account for current speed and direction and dirty air.

Whaaaat?

You are describing footing to a lift, not a header. A left windshift on port tack is a lift, not a header. This makes your math backwards.
Saling basics. Think in ladder rungs and leverage. You gain leverage in alternating wind shifts by moving sizeways more, footing. Always sail the lifted tack.