I am planning to build a 12' long by 3' wide raised bed oriented with the long side East-West with a trellis on the North side so that I can have a big 12' long vertical growing area with some shorter plants in front. I figure I probably don't want to go wider than 3' because I'll only be able to reach in from the South side once things start growing on the trellis. Does that seem about right?

As for the trellis itself, I was planning to use metallic conduit as the frame, with one long beam supported with hoops every 4', and hang nylon trellis netting (the kind with big 6"-7" openings) from that. I plan to grow heavy things like melons and squash, along with lighter things like tomatoes, pole beans, and cucumbers. Is the netting going to be able to handle being 12' long from end to end? I think the frame will take the weight, but I'm not sure about the netting. I've read that you need top and sides of the netting both supported. Mine would be supported top and sides, but with 12' in between the sides, I am a little nervous. Has anybody done something like this before?

I think I'm going to make the trellis 5' high. Given that the raised bed puts the surface of the soil at about 20" off the ground, the top of the trellis will be almost 7' off the ground. I don't want to get on a ladder to harvest, so my pole beans are just going to have to cope with being 5' and no higher.

Any other ideas?