Up until this weekend, I had been using SlimServer with firmware v.15. I had also, for a while, used the Inguz plugin successfully with that setup. I have no idea how things might have been different if I were using SqueezeCenter. I've only just changed to SqueezeCenter, but I also updated the firmware to the lastest one and I no longer use Inguz. So I'm not sure whether my experience is of any use to you at all.
Chad