Cut the drain line !!
Yes I cut the drain line, it runs down the inside of the rear panel and then goes into a rubber fitting that goes behind the rear fender, unfortunately it is glued into the fitting so I could not pull the plastic pipe out. As I could not get to the rear drains at the top (underneath the sunroof) or from the bottom (behind the fender) I drilled a small hole in the tube and tried to run the weedwacker wire up to clear the blockage but it kept hitting something before it got to the actual drain, looking at the plastic tubing it is about the same size as flex irrigation tubing so I decided to cut the tube with a flex tube cutter and then I blew out the blockage by just blowing up the tube. The repair is just a straight piece of plastic hose as there is no pressure in the tube and I can pull it apart to blow it out again if I need to.