Okay let me explain a couple of things about cylinders. First off the smaller you go the more rows and columns you will lose. The reason for this is because the engine has a harder time drawing all those tiny triangles needed to make railings and small posts etc. Don't ask me why...I just read that somewhere. I think LJ posted that or maybe it was rgoer. So it defaults to a cylinder that is much more simple in design with less triangles. Now it actually doesn't look too bad ingame. I use the default if I'm making quite a few of them. If I'm making a ladder lets say, then I may want to add columns. Adding columns will make your cylinder more round but, is harder on the engine. To add a column just go to the curve menu....insert >
Now, as soon as you go under 12 units it will go to the simple form of cylinder. 8 units is about a good size for a railing or a small fence post. So you can add columns and rows if you wish....just be cautious and be aware it will increase your triangle count.
My kung fu is also very weak