Pull-up a palm tree, bring a bucket of sand, and a box of dates and we`ll begin!
In the old days,when................................., one used to roll up a piece of cord and tape it on top or underneath a control surface to act as a trim-tab, cutting the tape length to suit the balance you wanted, ie aileron requires constant pull force to hold wings level, add/subtract some tab. So, you can also do the same to both sides to stiffen it up if the control harmonisation needs improving.Some a/c have very blunt trailing edges for the same reason.