James wrote:
Thanks for the input Anthony, and your experience is interesting and on
point.

From all the input received here, I now have no doubt that I can span 20
feet easily, using #2 southern pine 2 X 12 beams , on 16 inch
centers.

I'd have doubts. http://www.cwc.ca/design/tools/calcs/SpanCalc_2002/
Choose US species and the loads you indicated - you can't span 20'
easily or even barely. Your house, your call.

R