There is only one study that i am aware of that directly supports the 5:00 suppression theory -- it is an old Lancet study in which 100mg of D-bol was taken in one does, in the morning -- no suppression was found even after several weeks of use in this manner.
It is well established that LH release occurs primarily at night, thus it would seem that having normal androgen levels at this time would would facilitate a normal signal from the hypothalamus.
Empirically, I and others, have observed a maintenence of testical size following this protocol.
And, in fact, this is how I personally use our topical prohormones most of the time. Application upon waking at 7:00 A.M. or so, a shower at 3:00 P.M.
It limits gains, but it extends the period you can be on without negative repurcussions.