Finally got the flap tube and front/rear elevator control tubes smooth. Most of the focus was on sanding the inside of the plastic bushings. The two inside front elevator tube bushings (that you can't remove) needed some sanding of the control tube itself - when received from the factory the tube would barely turn inside these two bushings. The tubes were in and out of the plane a countless amount of times with each small adjustment. Riveted in the front/rear control tubes with locking ribs. Connected the control sticks and the left/right aileron movement had way too much binding. With some tips from another builder found that the back L bracket that attaches to the spar with the four small bolts was slightly overbent causing binding on that back bushing. When pressing on it with a stick it became noticeably smoother. Removed and slightly bent that bracket. The second issue on both my control sticks were that the attachment points were slightly angled when riveted at the factory. I drilled out the locking collar so that I could move it and the bushing back slightly to be able to remove some material from that corner that was digging into the bushing. After a couple of cycles in and out of the plane with the sticks, got the left/right movement smoother. Attached all the push/pull tubes (but did not torque them down).