Is there a limit to the force of a spell a spirit can sustain? I cant seem to find any.

So, could a force 1 spirit sustain a level 6 spell for however long the services allow?

technically, yes.

Ok, does seem kinda odd.

I had assumed that the spirit had to be of a force equal to or higher then the spell it wanted to sustain.

But, I thought maybe I was missing something when I couldnt find anything about it in the rules.

Thanks