I didnt read all the posts so this was probably covered multiple times. One post did say, teach them why. This is the most important. as engineers, we are problem solvers, and have to understand why a decision is made, and what factors influenced those decisions. Dont ever think thier...
What is causing the time constraint? Depending on the application, you may be able to achieve enough strength for service before the typical f'c, or 28 day strength.
The center of the manhole is going to REFLECT the inverts. this is assuming no significant drop across the manhole. if you dip multiple inverts, and have the standard eccentric cone, there will be some variance in the dip. now, you will assume the surveyor accounts for this. but now, if...