Any time. And useful info to know about what spell you're aiming for!
So Enhanced Matrix will save you a thread (you probably already know this?), so you are down to one spell thread at Weaving Difficulty 13, for Damage Shift. It's a Circle 7 spell, so you'll have an Enhanced Matrix (which you pick up at Sixth Circle).
If you already have a use for Enhanced Matrix, you can always Reattune On The Fly against a Reattunement Difficulty of 20 ... better than risking a 26, but if you need to swap spells, doable with Step 17 with Step 4 Karma (total Step 21). Still, that takes a round, and you still have to pre-weave the thread, so not that great if speed is an issue.
Definitely look into picking up some Enhanced Matrix Objects. Extra spell matrixes are a good thing, and if you're tight on Enhanced Matrixes, at least until Eighth Circle, it's a way of adding a bit more spell capability.
You may have considered all this anyways, but just throwing it out there.
Hope this helps!
Take kaer, James