Every build is a little different so that is really hard to say for sure. I think you would be safe with 1500 mm/m as long as your build is good and you don’t have any super high spots on your spoilboard.
Tramming the router makes sure that the router is exactly (well as close as you can get it) inline with the machine. If it is off in any way, a bit the size you are using will leave cup marks pretty bad. Usually you can use a few pieces of painters tape to get it in line. I will see if I can find the thread where we talked about it a good deal. There were even some custom mounts made to make the process easier.
Here it is…