Requisites with a Deficient Art

I should know the answer to this, but I've never played a magus with a deficient art before.

When calculating the lab total and casting scores for a spell where the a requisite art is deficient, is the relevant total halved? I'm thinking yes, but can't find a rule.

What about a spell that only has a casting requisite? My thought is the lab total is not, but that if you use the requisite to cast then the casting score is halved.

Can anyone point me at the rule on this, or is it just common sense?

You halve the totals (lab, casting), this is in the description of the flaw itself, on p. 53

They do, per p. 114-115, last of second to last bit in the frst column on p. 115. Buried far too deeply in the text for my tastes.

p. 53
p. 115

Thanks. I can't believe I missed the definitive answer on page 115, I swear I read that section before posting.

I read that section twice and missed it.
My local saga was about to house-rule on the matter, when I went back and read it again and found it.

Now, despite have a note on where to find it, I still had trouble finding the exact bit.

Far too deeply buried in the text for my tastes.