I reinstalled the leading edge and the tank to set up for drilling the W-423 join plate. The plans say to ensure the tank and leading edge fit is perfect before drilling. The leading edge and the top of the wing were a perfect fit right from the start. On the bottom of the wing I noticed a gap that started about 1/3 back from the leading edge and slowly got larger. My initial thought was this was caused by a cleco that wasn't seated through both the skin and rib, so I proceeded to remove and reinstall cleco's up and down the joint. This did nothing to the gap, so I removed the leading edge and tank to look for other causes. Reinstalled everything with same result. Finally looked at alignment of the outboard tank rib and saw the flange was sticking out past the W-423. Removed the rib, found that the flange was no longer at 90 degrees after fluting. Re-bent the flange and reinstalled all which closed the gap nicely. A lot of time consumed. Match drilled the W-423 through the tank skin, removed the tank then drilled and deburred all the holes on the top side of the tank.
