Absolutely seal the hinge gaps. That is a necessity. I use Dubro clear hinge tape and seal them from the bottom, but you can use a strip of covering if you want to. Before you connect the control rod put the tape on the control surface and the stab or wing making sure you follow the bevels and tuck it into the groove so you don't get any binding on full deflection. It helps if you fully deflect the control surface as you are placing the tape and tuck it in with a putty knife or something with a similar flat, thin surface. When looking at the end of the wing or stab, your tape should follow the "V" that is formed by the hinged surface.

Hope this helps,

Ken