OK, you remember the advice about pushrod connections that goes something like, "always connect your pushrods to servos and horns to give a 90degree angle".

There is a really good reason for this. It's why everyone with any building experience has heard that rule more than once, and heard it said in a number of diffrerent ways.

If the pushrod doesn't make a right angle to the servo with the servo arm or to the hingeline with the horn, the deflection at one end of the pushrod won't be the same deflection at the other end. It's been proven over and over and over. And the people who designed your biplane didn't seem to get it.

Here is a sort of useful picture to show conceptually where the pushrod ought to go and where the connection points should be. The green dotted line is what would give uniform deflection top to bottom. The black dotted shows an often used layout that really won't give you uniform deflection.