I've looked at field size, especially with a system that is based on Win% and it only showed a POT when the field size was less than 12. To me this wasn't logical, and it took a while for the penny to drop! There are multiple selections in the bigger fields, especially during the Spring Carnival.

I have a system to cull multiple selections down to one which include selecting horses from QLD, WA SA or NZ and culling the locals, purely based on the premise the "outsiders will be better than fair value.

I just don't see field size restrictions as a logical filter, although many do, esp bhagwan.