Thanks Ingvar - You are right, I found that 60Hz was too low.

I tried DT's MIBAM but for some reason it kept crashing the compiler. So I ended up implementing MIBAM myself at 90Hz (including the mirror image, so equivalent to 180Hz standard BAM) and am quite happy with the result. 30 outputs, 8-bit resolution running on an 18F4550 @ 48MHz.