>Hi.  I was wondering if anyone with a three story cage has ever had a couple
>sparring fuzzies take a tumble off the top level.
 
No.  We prevent it by arranging the shelving and hammocks so no drop is too
far.  Your cage dimensions are identical to ours - a "cat cage".  If it
really is the same as ours then the shelving hooks onto horizontal wires
that are spaced about 4.5" apart vertically.  We put the litter box on the
floor.  9" above that is a fully shelved floor with one 4.5" dia hole in it
that they climb up through.  (This isolates the litter box completely from
the rest of the cage.) That's the sleeping area (has a "house" on it).  Ramp
up 9" more to a 12" x 24" shelf for food and water.  Ramp up another 4.5 "
to another 12" x 24" shelf with a split level step up 4.5" to a 24" x 24"
shelf.  One 18" x 24" hammock above that.  The result is that its impossible
to fall further than 13.5" - that's the longest straight drop.
 
>We are thinking about buying a three story cage (36"L x 24"W x 48"H) but
>wonder about the safety hazards.  Also, would this be big enough for 4
>(maybe 5) ferrets?
 
Fine.  We have five in ours.  In fact most of the time they all sleep in the
same place - either all in the hammock or all in the house.  (The house is
12" x 24" x 6" with a couple of 4" entrance holes and when five fat ferrets
get inside its 13 lbs of almost solid ferret inside but they seem to love
it!)
 
My experience has been that if there is any spare space without either food,
water or bedding in the way then they will convert it to a litter box.  I
originally tried leaving large floor areas for "play" but all they did was
take a dump in the corner and then go back to sleep some where else.  I
recommend making it obvious what you intend them to use any floor space for.
i.e. either place food or water there or put bedding there.  If its a bare
area one of them will use it for a toilet, particularly if the proper litter
box has been used by someone else!
 
(I'll send a gif in a subsequent message to illustrate.)
[Posted in FML issue 1980]