>
>In terms of pali, what were the common usages for piti and sukkha,
>and how exactly did the Buddha mean those terms to mean in a
>buddhist context?
>

Have you read Bhante Gunaratana's book on the Jhanas? It has sections
discussing piti and sukha:
http://www.saigon.com/~anson/ebud/jhanas/jhanas03.htm

The fundamental category difference he takes up is that piti is a
vedanaa, while sukha is a sankhaara. From his description there I
wouldn't say that one is mentally and the other physically based.

I'd also be interested in any observations people might have about
the first part of your question. To find common usages it might be
necessary to look at sanskrit equivalents, since there's so much more
secular literature there.

Your question seems to be asked from two different directions: on the
one hand you want a definitive ruling. For that you just need to find
and believe the orthodox opinion in the Abhidhamma. On the other hand
you wish to empirically study the terms in natural contexts. These
two approaches might collide, but it sounds like a very interesting
study.

best regards,

/Rett