Wide pvc boxes

How are you planning on building it? Are you using something 20' or building it with smaller stuff like 12' 2x4s or using 8' ply as a top? If you're using 2 pieces to get the length you can make one slightly higher and make that the permanent front end and you'll never catch. Even if you had a flat 20' to screw the pvc to you could slip something underneath to raise one end up slightly.It doesn't need to be much at all. Also if they're pretty much even you could use a razor or knife and bevel the edges of the pvc. That said idk how even you'll end up with and you could break yourself if the end pvc is higher than the front.

Well I am using 10' 2 by 4's to make the frame of the box so I will have to just make one raised a bit more. I think it would actually be more fun that way

It doesnt have to be much at all. Just enough to grt across smooth. Like a 1/4 or less even