One thing to remember about multiple carpenters is that they sometimes interfere with one another (for lack of a better thing to call it). I've especially noticed this on Obelisks (and maybe Sphinxae -- I don't know if that's the plural, but it looks good). With Mausoleums, I haven't been able to tell, and I don't think I've done a Pyramid since I first noticed the problem.
Since getting the scaffolding or ramps built is one of the bottlenecks to monument construction, having more than one carpenter ought to speed things up, right? Well, sometimes it just leads to wasted wood (which is morth more than gold) and time.
Everytime two carpenters have arrived at an Obelisk at the same time, or the second arrived while the first was still working, I only got one section of scaffolding from them.
This is the 'micromanagement' technique I use to get around this problem. It relies on the huge amount of time it takes a carpenter shop to turn wood into 100% complete scaffolding. There are two, actually:
1) Place one carpenter near the worksite and one fairly far away. If they both set out at the same time, by the time the farther one gets there, the first has completed his work.
2) Build one carpenter always connected to the road network and one not connected. The one which is connected will get a new delivery of wood as soon as a carpenter leaves (naturally, there is SY cartpusher transit time). The carpenter not connected to the road network will get a new delivery of wood only if you make a temporary road connection.
This technique works because you 'juggle' wood deliveries. That is, allow a delivery of wood to the disconnected carpenter only after the connected carpenter is 50%-60% finished with turning its wood into scaffolding. Once the cycle is established, it's possible to allow the disconnected carpenter to have a second delivery. Because of the huge amount of time needed to turn wood into scaffolding, the two carpenters shouldn't interfere with one another.