Although the raised rail appears to be decorative it actually serves to stiffen the trailer. The plans stated it should be added to any trailer over 18' or using the "V" shaped cross members - mine is both. It also offered the option of using either ½" solid round stock or ½" black pipe to form these. I decided to use the round solid stock (cheaper) but if I were to do it over I think I would choose the pipe.
The round stock works fine and provides the strength needed. But my concern is that eventually either myself or someone else will use it as a step when accessing the boat while on the trailer. If you step directly on top of on of the vertical supports it would be no problem but standing in the middle could cause it to bend down and detract from the over all appearance. I think the pipe would be stiffer and less likely to bend when this happens - and it will! Another possible fix would be to place the vertical supports closer together than the 2' called out in the plans.