First thing, before starting your full lab, make sure that the Idle PC Value for each type of router is well calculated.
For example, I added some 1710s as PCs for my lab:
1. all lab should be shut down, except one 1710 routeur.
2. start it
3. log to console, wait until it loads completely and enter privilieged mode
4. check your processor consumption. In Windows, it’s with Task Manager. With Ubuntu (my favourite), with System Monitor -> Resources:
7.repeat these steps until you get low processor consumption: