Might have wrong end of stick here but if you are doing this as a line the lead rider rolls to the side and backs off, the next rider does *nothing*, they maintain exactly the same speed, the former lead rider just rolls to the back and drops back in as last wheel. there should be no acceleration by the second in line rider once the lead pulls over. If the lead rider gets too slow then second in line just says so and that is the nod for whoever is first wheel to roll to the side.
Also if I was the coach I might let you do a k on the front each on the way down, but on the way back at the business end no way :-) 18 minutes recovery is too much if you want to do this as a time trial and as fast as you can. Shorter more sustained efforts on front are what you need at the business end. Drop the km marker (1 k down hill does not equal 1 km up hill) of effort and only use time, 2 minutes, on way down, perhaps 1 minute on way back.
Would play with this on beach road one day, just get everyone to do 1 minute at a pretty high effort, hard enough to be seriously hurting by the end, but enough left to be able to grab that last wheel and recover....
I'll shut up now.