Crazy Eddie wrote:
Seems perfectly plausible to me
I don't think so. Mr Scott's Guide...
is unofficial. All 'more-or-less official' books after TNG said that transwarp was a failure.
Actually, the TNG tech manual is the only one that claims this, as does the Star Trek Chronology which uses the TNG manual as source material.
And as already mentioned, there's ALOT in the TNG manual that is either apocryphal or self-contradictory. It's an interesting read, but not much more than that.