I used 10 on mine and never had a problem. My Avistar took a beating on the leading edge during my training period. I let it go for a while because the monokote was not torn and it still flew fine. I finally took the time to make repairs in 4 areas where the LE needed fixing. Depending on the amount of damage, this may not be the way to go, but it worked for me.

1. I cut out the bay in front of the spar where the damage was. I removed the covering and then cut along the sides of the bay leaving an open area between the ribs.

2. I traced out a pattern of each rib and cut it out of a 3X5 card. Then I transferred the outline to a sheet of balsa that was thick enough to add strength to the ribs one either side. (I made the extra rib just enough smaller to accommodate the leading edge sheeting when it was replaced. You need to leave this space, or you will not match the surface on each side when the sheeting is added.

3. I purchased a piece of leading edge balsa at the LHS and cut it to length between the ribs and glued it into place.

4. I glued in the balsa copies of the ribs on each side ensuring that they lined up with the sheeting on each side. This included checking to ensure that the bottom and tops followed the underside of the sheeting material that was still in place. The ribs also met up with the back side of the LE to help have something to glue to and add strength.

5. Glue another piece of square balsa in front of the spar so that the sheeting has something to glue to when installing.

6. Install the sheeting top and bottom bringing the sheeting out to the point on the leading edge. (I had to glue one into place, trim the front back to the LE balsa, and then installed the other.

7. Sand all parts until smooth and matching both sides, then re-monokote with same color.

I did this same procedure in 4 different bays in the plane and when covered it looked just like new. There may be a much simpler way, but this worked well for me. Of course, I spent about 3 weeks redoing the 4 places, took it out to the field to fly and after 11 flights I hit a bird and the plane was destroyed. I don't even want to know what I paid in time and money for those 11 flights.