I always stored mine down, never had much problem, possibly a little rust where the disks went into the gravel floor. 

I talked to a neighbor that didn't like the flexible hose arrangement, and he installed sliding tubes.  I did some google search to find such a thing, and don't find anything.  I don't even remember which neighbor had them now, but I saw them.  I kinda think he made them himself out of different sized plastic tubing, and used the cut-off rubber tops to attach them to the seed box.  I wasn't all that impressed, since I didn't have much of a problem, it seemed to me he might have more problems on uneven ground with the solid tubes telescoping if he ran over an obstruction that jumped the opener up quickly. 

I would have responded quicker, but I was still trying to remember more details about the subject, and whether the sliding tubes were commercial or home made.