Help making Powers and Threshold Magic work together

[Kesendeja]

At the prompting of the magic user in my group I've started looking at Threshold Magic.

I think I understand how it works, but how is the threshold to activate the spell determined?

I don't particularly like standard magic and would prefer to use Powers as Magic to make them. How would determining the spell threshold be handled?

Finally how does the Mana Level of the setting affect the system?

I may have completely missed the answers to these but I haven't found them either in book or on the forum.

Any help is greatly appreciated.