So, I've just been paging through the Words of Power portion of Ultimate Magic and I'm quite impressed with the final product. I particularly like how the effect words combine (much in the same way the CR system works) to produce spells.
I do have one question though. The system obviously uses two mathmatical ways to combine effect words with respect to their level. A spell of level k can be made up of two spells of level (k-2) or by two spells with levels (k-1) and (k-3). Is there any particular reason why other combinations of effect words can be used beyond those shown in table 4-1?
For example, we should be able to make a 6th level spell out of effect words with levels 4,3 and 1 but this combination isn't listed in the table. For that matter, does anything break if we allow four level 1 effects to make a 5th level spell?
I can understand that limited combinations which can be looked up in a table is easier to use, but the system seems like it should be robust enough to use in this way.