Add to the above, research how the sun is at different times of the year and how tall the plants are likely to get. 3.5' would not be sufficient for tall crops, and they would shade out the lower growers, so would need to be the farthest from the sun. It will be a learning experience for you, but worth it. I would think two beds with paths down the center and on each side for access, but that would depend on which direction you faced the green house when you build it, and the seasonal vegetables you want to grow. Follow the sun and make yourself a diagram that you can turn as the season changes. then start researching what you want to grow in each season. Most winter crops are relatively low growers, but summer crops Can be tall. Also keep in mind that flowering crops need pollination. Lots of thing to learn, but you have long winters to read and plan.
