Post and Pier Beam question

[yarnfly]

As previously mentioned I am building a 16X20 cabin.  12x20 with 4 feet of deck making the 16' balance.
I have decided to go with the post and pier foundation method.  My cabin will essentially be a single floor with a loft one one end 8 x 12 in dimension.  I was thinking of running 3 beams of 20' under it but am not sure how to do it or if I can go with 2 beams.  My initial intensions were to go with a 2X6X16' on 16" center floor with the 3 beams.  My span tables say I can go 2x6 with bridging for 9.5 feet of span.  But...will I experience a bouncy floor.  Should I go 2 x 8 x 16' on 16's.  If I go 2 X 8 can i go to two beams underneath?
How many support posts will I require with the 3 beams and or with the 2 beams.  Can I use 4x4 posts or do I need 6x6?  How do I size my beams.
Sorry for the plethora of questions.  I thought I had it figured and then I talked to someone and got worried.
Your help is appreciated.  Better to deal with this now than come construction time.
Best regards,
yarnfly

P.S. I added this pic of the proposed cabin. I am going to attempt to build this one without any plans.  Hope the pic thing works I never seem to have luck with it.

[jonsey/downunder]

I would think that 6x2 floor joists would require 3 rows of bearers. John would be better able to direct you there. I have no idea of the code requirements in the US. But please, please, please draw a plan. It will help you understand how the whole thing goes together, how things fit, and save you time and money in the long run.
In my own house, I spent about 12 months working on my plan. I got to know how the whole house would be built, how airflow would work the sun angles, everything about the house. I got to know that plan so thoroughly that after setting out the foundations and floor I have hardly looked at it since. Worth every minute.
jonesy.