Unfortunately Sunline VINs don't decode very cleanly. The two big things it tells are the model year and approximate overall length of the trailer. It also tells the number of axles, rough box length (in 2' increments, Sunline never published the exact number), manufacturing plant, wall construction thickness, and model line, but most of those are pretty irrelevant for determining a floorplan. The model year codes follow the standard NHTSA regulation shared with cars and trucks where A=1980, B=1981, etc., so those are easily found online. Unfortunately since Sunline closed in the 2007 model year, the final year code used was 7, and so we never saw any duplication of a year code from 2010+.
Determining the Sunline model floorplan number based on a VIN only is very difficult and impossible to explain in a single post. There are some models in some years that it's easy because they only built one floorplan around that size. Others had anywhere from 2-6 floorplan variants that the only way to know what it is exactly is from pictures or seeing the trailer in person.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9473.8 (as of 6/18/21)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR