Nicostoffi-Hi I would rebuild the retract bays anyway if I were you.I installed Robart retracts in mine and the space between the false ribs was not big enough,so I cut them out and boy I'm glad I did. The glue they used was not very good and they came out real easy,never would have held up to a rough landing.I then cut down through the spar enough to clear the air valves using a Dremel tool and a spiral cuting bit.You should now have aprox 25mm of space between a main rib and the edge of the cutout in the wing.I used the ribs I cut out as templates, to make new ones out of 3mm plywood,keeping in mind that you have an inner and outer rib.I spaced these new ribs off the main ribs with 10-12mm hardwood blocks cut to fit tightly from upper to lower sheeting then I epoxied to them to the side of the main ribs. To those I epoxied the new ply ribs,and then I cut out ribs out of 10mm hardwood and epoxied those to the side leaving the bottom of those ribs flat to attach the landing gear too. I wish I had taken pictures of the whole process to show you,but I think you will figure it out.These babies are solid and the whole process took about 4 hrs including figuring out what to do and looking around my shop for materials.Good luck and watch your back! Oh by the way what part of Germany are you from? My wife has family in Munich.