Some info on Pegasus stash...
There most definitely is at least one stash roid with various goodies (3,4 and 4th gen ships, guns, missiles and other) in the same cloud as stash nav point. Just go up and ascend a bit. It is one of the topmost roids (with the red light).
As most stashes it's load is decided on sector entry, but you can bee-line straight to it before going to Paymaster so you can get the stuff you want without wasting "too" much of your time.
On to the other stash...
The quest stash from the transports is NOT decided on sector entry, but on spawn. Just save before going back to Paymaster's station. There are of course two fights standing between you and the transports, but easy enough to to go through them couple of times.
There may be more roid stashes (the script file suggests so), but I cant find them, just lot of fakes.
And on the matter of Hep system stash...
While going through the scripts I found that the condition making the stash appears is achieved after returning to Placid something Station after Elio. An indication of the condition being true is the change in your mail (the one from Ternie starting with "Great Partner!" or something like that is deleted)
Lastly...
WTF is this?
http://www.glowfoto.com/static_image.../img6/glowfoto