It's interesting that there can sometimes be more than
one "opposite" to a word.  While I was atempting to
discover which verb roots are necessary and which can
be formed by a negating prefix on the root, I noticed
that I need two different negating prefixes, one for
"un" and one for "not".

consider these opposites:

take <-> not take (refuse)
take <-> untake (give)

make <-> not make
make <-> unmake (destroy)

know <-> not know
know <-> unknow (forget)

do <-> not do
do <-> undo

This seems more like the three points of a triangle
than the two endpoints of a single spectrum.  Yet in
other cases these two different opposites really mean
about the same thing:

welcome <-> not welcome
welcome <-> unwelcome

happy <-> not happy
happy <-> unhappy

In other cases they mean three different points along
a single line:

fast <-> not fast (but not necessarily slow either)
fast <-> slow

Anyway, so far it looks like about 10 to 20 verb stems
will be all it takes for Lepayu, my conlang with
"split verbs", since each sentence has two or three
verbs their individual meanings contribute to the
whole meaning of the sentence and with the right 20
verb stems that's 20^3 = 8000 different possible
meanings.  I just need to find the right 20 "primary"
verbs, which like the primary colors can be blended to
create any color of meaning.