dubious new Nine phonology

I was thinking about  Nine, and I could only come up with a phonology with 8
phonemes (but I'm not sure whether I'm cheating with the vowels).  here's my
idea:
p, t, k
u, o, @
n, r

[n] before a single plosive becomes allophones /m, N/, so [np] = /m/ and
[npp] = /mp/.  [n] after a plosive creates a voiced plosive, so [pn, tn, kn]
are /b, d, g/ and [nppn] is /mb/.
[r] alone is english [r] (/R/?).  after a plosive it becomes a trill, so [pr]
is an unvoiced bilabial trill, [tr] is an unvoiced spanish [r] and [kr] is an
unvoiced french [r] and [pnr] is a voiced bilabial trill, [tr] is a voiced
spanish [r] and [knr] is a voiced french [r].  [rn] is /l/.
[p] before another plosive is /f/, and [t] before plosives is /s/.

my major concern is with the vowels.  front vowels are formed by combination
of two schwa and a back vowel or itself, so:
@u - /i/
@o - /e/
@@ - /a/

[@u] (/i/) and [u] become semivowels before other vowels, so:

@u+@ - /j@/
@u+@@ - /ja/
u+@u - /wi/
etc.

In this system, the following words fit my tastes:

pn@ifkorn@u@onp - /bifkolje~m/
ttonttnu@u - /sto~ndwi/

I have no idea if this fits into the category of allophony, so if not please
correct me.

Joe Mondello