RE: synchronizing engines
The best advice I've ever seen was to make sure the engines are each, individually broken-in and tuned for maximum reliability. If you can get within 500 RPM or so, you're good. If you have too much variance, then your props may not be quite what they're supposed to be or the odd engine is not right. It's better to discard the engine and replace it with one that will turn where it belongs than to risk such a wonderful model. The cost of a new engine will be far, far less than the cost of the model.
Reliability is what your main goal should be.