Did the books ever mention whether or not slipstream technology was something the Federation had developed prior to Voyager's return from the Delta Quadrant?
I remember some discussion of this quite some time ago but not how the conversation concluded. On one hand, the first sustainable slipstream that I recollect we've seen is from Voyager's "Hope and Fear", but I don't know off the top of my head if this episode occurred before or after Voyager lost access to the Hirogen comm network that had allowed it to link back to Starfleet. On the other hand, Voyager returned to Earth a very short time before the Vesta- and Meerian-class ships came into service, suggesting that either Starfleet had been working on slipstream for long enough to put these classes into production, or these were pre-existing designs that just happened to be wholly compatible with the slipstream tech that Voyager returned from the DQ with.
It's kind of like, which came first, the chicken or the egg?