And in my experience, if more than 5 people are working together to do the same thing, one of them is going to be the manager, whether you call them that or not. We do it intentionally and explicitly because that's more likely to lead to a good manager then just letting someone take charge.

I don't think that contradicts what GP is saying, or perhaps I misunderstand them. 5 directs per manager. So 10 engineers = 2 managers. But at 25 engineers you have 5 managers, and now you've maxed out their manager.

Either way, my experience has been 5-10 directs as the sweet spot. 12-15 is fine but really pushing things. Beyond that, you need more structure.

Cars and planes made multi site management more effective.

Phones, cellphones, email, etc have all made management communication more effective. Address book in your iPhone is faster than your secretary, a Rolodex and the switchboard.

Automate the easy stuff, and have the management do the human leadership tasks.

I’d ask the engineers what else can be done differently but maybe you have implemented lean leadership already.

Beware a thing: the classic production of the '900 manufacturing industry do just require organization because anything is done on the assembly line, but creative works (witch means anything not already designed and now in mass production stage) is another thing. You can't subdivide a problem in tasks effectively until you figure out how to solve it in the first place, you can't easy share ideas quickly without "work's social life" etc.

To be more precise, it's doable but demand years of experience, our society except for very few jobs lack such experience and as always anyone want young people with decade of experience behind...

You no longer have to spend 5 minutes walking between meeting rooms and can now go straight from one meeting to another with no time to collect your thoughts at all!

I understood that as 18-24 engineers in a company, not per manager.