My work and play has leaf springs, and the springs are under the axles. It may be possible to do what is called, flip the axles. The axles don't flip, but instead spring perches must be welded to the top of the axle, and the the axles moved to below the springs, instead of above. Do a search on here, and you will find several post on other trailers.
I changed the title of the tread, because read it to be a concern over plumbing. I will change it back.
Lastly, if you do this, you will have to change your hitch set up, not too hard. Also, maybe more of concern, what are you hauling? If you raise the trailer height, you will increase the ramp angle. $ wheeler, dirt bikes, won't matter as they have plenty of ground clearance. A low Harley, or Goldwing, may high center when it breaks over the top of the ramp. Not a good place to be stuck.
Here is one thread may help:
Flip the axles