I stumbled across Robert Oster and his signature inks on eBay recently, see here.
This is the front of a rather ordinary copy paper - Australian Reflex from some years ago. It is somewhat absorbent, so the dry times are really fast. However, even on this paper, there is no feathering or spreading.
I am showing the back of this scan to show that there is some spotting of bleed through that is visible, but they are otherwise a very well behaved inks.
This is the front of a better quality paper, Fuji Xerox Sustainable Earth copy paper. It is no longer available, but it is comparable to Double A, Kokuyo Campus or Nakabayashi papers. You can see that shading is more prominent on this paper.
I haven't shown a view of the back because there was nothing to see. No show-through, no bleeding, just white paper.
This is Tomoe River paper, but given that the ink behaved so well on the FX paper, there is not much improvement here, however the dry times are substantially longer.
This is the back of the TR paper, demonstrating the show-through that is synonymous with this paper. What looks like bleeding just above seems to be an artefact, as it is not visible on the paper.
Other notes --
The ink is reasonably saturated, but seems to have little surfactant. The Bondi Blue in particular has a hard time wetting a freshly cleaned nib.
The first scan, on the lined paper, was done with the two Jinhao 599 pens that came with the inks. The other scans were made with a #6 Chinese nib fitted into a dip pen holder.
Currently the vendor only has international shipping options on one ink, the Yellow Sunset. I don't know if he is willing to add that to the other inks, but if you aren't in Australia, and you are interested in the inks, just ask him.
The two inks I have tried here are worthy competitors to the Blackstone Colours of Australia inks from Justwrite in Brisbane - Sydney Harbour Blue and Barrier Reef Blue. I don't think it is a matter of either/or, but both.