Group time trial

I was wondering at what % of FTP you ride in a 1 hr team time trial of organised group "tempo" ride.
e.g. 5 men means i'm in front for 1/5 of time, let's say 10 sec. and recovering for 40 sec.
How many seconds should you do in the front if you ride with only 3 of 4 guys.
perhaps someone can make a table or has a table like this
2 men : x seconds in the front : % FTP in the front
3 men : y seconds in the front : % FTP in the front
...
...
of course every one should be at same level I think...

thanks
poulidor : always second