One thing I like(d) about both the slingmesh and regular RANS seats was that you could actually turn the bike upside down, using the seatback for support -- make it handy when having to change a rear tire/tube.  NOT so much, with the Hoagie seat...  having the bike laying on the ground when trying to pull or reinstall the rear wheel is a hassle.
 
It occurred to me that, perhaps a support of some kind could be cobbled up that would insert into the ADEM headrest support slot, since the headrest is mounted on a metal bar that stays in place (up/down) by velcro.  It would use a similar metal bar to go into the support, but have two arms that could unfold (?) into a "Y", locking into place to support the weight of the bike while upside down.  
 

 
Shouldn't be too heavy...  I've got a couple ideas...  hmmm......  I'm thinking something with two angled receptacles that would hold two pieces of fiberglass tent pole??