No experience with managing them, however I was was involved with a large build. This was just a huge project for an LLL.com with projects on various sub domains (inividual sub sites), so not sure its the same thing as you mean.
However, the biggest mistake she made was interval payments, so a build time (staged) over 18 months, and payments were due every 3 months. Payment was done and dusted but the project dragged on, was nearly 3 yrs before completed, and even then it were full of bugs and issues. Without the financial incentive she has a nightmare pushing them, non stop excuses.
While setting them up, I would stipulate payment is goal or target related, basically keep the carrot close to the whip. Hopefully that's around about helpful.