Of course the big difference with gating Iron and Ally with reference to either gating into the hub from underneath or just pouring straight in through the top is that the sand floats very well in the Iron, which means the longer your runners the more chance you've got of picking up sand and of course the iron cooling on it's way in through the long path, while pouring in through a central riser sounds like it will break up the bottom of the mould this can be averted by fitting a solid ceramic/graphite plate at the bottom of the hub so that the sand doesn't erode in the initial part of the pour, keeping in mind that whether you pour into the centre or into a horn for an under feed the metal still has to drop a long way onto sand in the early part of the pour, when we did track wheels at the Steelworks foundry it was straight down the middle, with a well at the bottom and the ceramic plate to prevent breakup of the sand, we also used a crane to pour as we were talking about 100 Kg final component mass, so 150-200 Kg pours at least, so well out of hand pouring range.

I was looking at the last photos of the pattern and I realised that beyond the Alloy wheel comments from before, it looks a lot like a nut bowl that my Gran used to use at Christmas, where each section had a different type of nut or Sweet in it, so do try to keep it clean and you've got a very usable nut bowl for when we all come around

Regards
Rick