So I got one of these on closeout from Joebob's http://www.joeboboutfitters.com/KIES_Free_Float_Rifle_Length_Handguard_p/kies-mk1ff.htm

It came with one 3" rail section, and I would like to get some more. Searching around online and can't find rails from KIES, so I am wondering if anyone has tried other brand rails on this. The mounting holes are 5 slots aparts.

Also I am wondering if there's a way to mount a full length top rail. There is a hole in the back of the rail meant for set screw but I don't see why it couldn't be used to secure the rail. If anyone has experience with this handguard..please help

Did you try the YHM rails for their customizable free float handguard?

Thanks for the idea. Checked them out, but the screw holes are 2 slots too far apart.

Update: Looks like Diamondhead accessory rails would fit, but I don't think I am going to even bother.

The tube itself is fine, but the barrel nut that it came with is a total POS. When I raised torque wrench setting to 80ft-lb to time the nut, the teeth broke right off. I managed to get it aligned with remaining teeth carefully, put in set screws and called it a day. It's been used on a 22 upper so it won't be taking too much stress anyway, and I don't plan to take it off again.

Had one of those in the cart and was going to get it with one of their lowers and changed my mind due to their billboard logo on it.  
After reading about your troubles I am glad I did.