my 150m time is 18.6 seconds. My coach is really good timer, is off in electronic times by .3 always for 2 years now that i know him. He never makes mistake.
If he's always 0.3 seconds off he's actually a worse than average timeer (albiet a consistent one).
Another thing i am fixiated on the last 40m now and been doing calculations and alot of amateur runners run the last 40m of 100m in 4.2-4.4 seconds the ones with good speed endurance like my friend clocks electronically 3.8s for last 40m.
I doubt there are many 11 second 100m runners who are running 3.8s auto timed for the last 40m. This is something characteristic of a mid-to-low 10s runner.
This is very interesting if i run 7.50ht and can hold the last 4 seconds its 11.5 which is where i am running man if i can drop those time to a 3.8 thats 11.30 right there.
As Davan said you may make the biggest impact on your last 40m by increasing your top-end speed. The faster you are at top end speed the further you can decelerate while still running relatively fast.