Sources for fabric/other questions
I am not a canvas expert, but in reading opinions from experts, Sunbrella seems like a no-brainer. Sunbrella withstands UV from sunlight very well. We also use the teflon thread that also withstands UV very well--extremely expensive, but again will not degrade in a reasonable time. Doing canvas is so much work, that it is a shame to have to re-do it later when it fails because of exposure to the elements. We are in Florida and headed farther south, so sun is an issue. If you were in Maine and put the boat up under a plastic tarp for 8 months of the year, it might be a different story. Also, the last bimini on the boat, which was on there when we bought it, failed for UV degradation, which is what generated this project in the first place.
I cannot vouch for where we got the sunbrella, but I did get a good price, good delivery, received what I ordered, and got crisp, friendly, quick customer service. I only did 1 or 2 orders this last spring, however, so my experience with them is not extensive. But I got a really good price and was very satisfied with the transaction. The email is "firstname.lastname@example.org", I dealt with Sam Frusterio.
For most of my other stuff, I have been ordering from Sailrite, since their customer service has been so great. However, their prices are not the lowest you can find, and on bulk buys, I did a little shopping.
Hope this helps. Others may be able to shed more light on the topic.