Analyze the 400m!

400m. If we look at Micheal Johnson, 19.3 for a 200m, and a 43.2 for a 400m. Roughly double the 200m time then add 4 sec. Same holds pretty much the same for me, though abit slower. So, in actual fact, the 19.3 includes the 1st 10m, which is around 1sec slower roughly than every other 10m effort, so, even if you done a 50sec 400m, in 25s 1st 200 then a 25sec 2nd 200m, you are still slowing down 1sec in the final 200m due to the 1st 10m start of the 1st 200m. Therfore, in actual fact, you are going to slow 5 sec during the 400m compared to the 200m race.
What about predicting the 200m race? This i have no details on. Just guess work. Say a 21sec 200m. 1st 10m = 2sec. then on average every 10m effort = 1sec. though how steady state would that really be? Last 50m would more than likley be slowing.
So, maybe, a 60m block start would have to be around 6.9sec, a flying 60m in 5.8sec. Are these goals worth shooting for? Or faster times? They would have to be pretty close? And these are just times to run a 400m time!!!