This is really more a quick opinion poll than anything else, but if you've got experiencing dinking around with these sorts of things, even better!

It seems like a common enough houserule to expand the dice pool used for Effects to be Arete Sphere, rather than pure Arete. How often this is backported from Awakening, and how often it's independently derived, is certainly its own discussion with some marginal relation here, because the meat of my question is thus:

When using that houserule, how do/would you handle the pools for conjunctional Effects? Arete highest Sphere in the Effect, or Arete lowest Sphere in the Effect?

Awakening does the latter, more or less, and I can sorta see the merit behind it. It doesn't lead to player/ST arguments wherein people are trying to cram unnecessary Spheres into an Effect to get more dice on the roll for it (such as "I cast this fireball a minute into the past so I can use Time 5 instead of Forces 3 as the added Sphere for the roll"). On the other hand, it also definitely leads to feel-bad moments where you're not trying to abuse the system, and you end up with a smaller pool.

In an ideal world, we could just take the average of all involved Spheres, but division is just... fundamentally not something RPGs should ask players to do on the fly, so the practicality of that as a solution is negligible.