Hi
Firstly:
DavidRedmayne wrote:
My boot drive has 10.58 Gb free.
You are heading for a disaster here; this is not enough free space for the OS to operate effectively. The exact numbers can vary, but typically the rule of thumb is 20% of the disk capacity as free space.
You really do need to make some more space, regardless of any Mainstage installation.
DavidRedmayne wrote:
Hi, the additional content manager is saying that "LogicPro and Mainstage Additional Content" requires 5.8Gb.
Yes, but you may well need double that whilst you are downloading /installing. (and there are the optional jampacks too).
You could possibly get away without installing all of this content, and you could (with some messing around), possibly move some of it to the extenal drive.
CCT