And some states require you to have a CDL. Also, don't forget that loading weight on the back of the TT (tongue weight of the 2nd trailer), will decrease the tongue weight of the TT which in turn may cause a sway condition.
I understand that you have a "Curt" weight distribution unit and I assume that it doesn't have any sway control built in to it. Do you have a separate sway control device or none at all? If your WD unit doesn't have built in sway control, before you attach a 2nd trailer, I highly recommend that you purchase and install a WD unit that does...ie: Reese Dual Cam or Equi-i-zer (brand name). If you have the bucks, a Hensley Arrow or Pro Pride will be the ultimate in sway control.
Check your state's laws on double towing before you go to any expence.
Good luck
Ron