I looked at my pics and I wrapped the fabric around the side of the cap-strip of #10. I remember wondering about that but I recall that I sanded the epoxy varnish to roughen it up a little before applying the fabric and taking extra care to make a good glue bond of the fabric and then shrinking it so that it was good and flat against the underside of the cap-strip. I then bonded the aluminum with 3-M and rivets. I used nut plates for holding the wing tips on for reasons stated by Papua.
I don't know about cutting the fabric off. There's only 1" of surface on the cap-strip for bonding too. That idea crossed my mind but with the ironing of the fabric to shrink it, the idea of the strength of wrapping around the cap-strip was more appealing to me. With all the bonding and rivets holding the aluminum strips on, I don't feel concerned that the wing tips will go anywhere.