They don't look like they would weigh all that much themselves and its the contents you'd have to worry about (is there a limit?). Depending on the configuration you select would affect the weight. For example if you installed the dual storage with the spare tire version, this would allow one to lighten the weight at the pin since it could be positioned where the existing spare tire area is located behind the axles like on my Monty (and yours).
If you are under your GTWR and the axles are still carrying what they are rated for, then I don't see anything wrong. The problem with where they are mounted is that when the rig is set up, the extended slides might make it difficult to get things in and out. A little advanced planning should remedy that.
Trying to mount this unit anywhere could definitely have difficulty because under my rig I have valve handles, suspension brackets and propane lines. The best place for me would be at the spare tire. The installation could be tricky anywhere but certainly doable.
We'd like to see your setup at your next show-and-tell.