The ColorMatrix1 tag looks fine in principle, you might want to lift the “10000 denominator” restriction in your implementation (i.e. read both numerator and denominator and do the actual division):
ColorMatrix1 10533639/8388608 -2310377/4194304 -5071987/33554432 -1063505/2097152 5631805/4194304 8584029/67108864 -2605039/33554432 4462193/67108864 4932553/8388608
IMHO, libraw should have no problem with those. If it does, it should be reported upstream…