[dataweaver]

There's also a Pyramid article in #3/44 called From Skills to Advantages, written by Dr. Kromm; you could use that as a basis for adapting spells for use as Knacks; though as Dr. Kromm said in that article, the result is generally too cheap for what spells can do.

Another approach would be to take the "1 character point = 25 energy" equivalence used in Devotional Enchantment (Thaumatology p.54) and apply it to the spell's item cost: so an Air Vortex Knack would cost 48 points (1200 energy). This won't be at all balanced against the Advantages system; but it's quick and easy.

Conversely, if SJGames ever publishes GURPS Magic Powers, one thing I'd like to see them do would be to go through GURPS Magic and redo all of the Item energy costs to conform to the equivalent Magic Powers point costs.