Hi Jim, that sounds like a fun project. I'm no engineer either, just someone who thinks he knows enough about wood structures to be dangerous.

Actually with Don P's patient explanations I have learned enough that I can work my way through your situation. As I understand your description the 6x8 beams will be supporting the trusses. Assuming full snow load and 10 lbs/sf dead load, the total load for the roof will be 50 psf. Your posts are 11' on center, so each beam will have a tributary area that is 11' wide and as deep as half of the structure width. I'll assume a width of 20' but you'll want to adjust this calculation based on the actual width. So each tributary area is 11' x 10' = 110 sf. Total load on a beam is then 5500 lbs.

Using the toolbox available on the left below the sponsor links, I'll use the

Uniformly Loaded Simple Beam calculator. Inputting values for load and length, we have 5500 lbs and a span of 132". Eastern white pine is in the 2015 NDS Supplement. A beam of EWP #2 has engineering properties of Fb = 575, Fv = 135, and E =1.1 x 10^6. Plugging that into the calculator, the max load the beam can support is about 2200 lbs.

Using those same numbers and making the beam deeper, a 6x10 can support up to 3450 lbs and a 6x12 can support up to 5000 lbs.

This is using the engineering values for #2 graded beams. Better quality beams are stronger and can support greater loads. Were I in your shoes I would look at going to a 6x12 beam or using a much stronger wood such as Douglas fir. Otherwise it's probably a good idea to bring in an engineer to help determine the best path forward.