Tricky transient problem

Following on with squash ladder project, I've come across a particularly patience ending problem. I need to display a view that contains a sortable column based on a transient property. My ladder needs to be sorted by winning percentage and this value is transient (calculated and not persisted). A google search shows me a few different posts but nothing that I could get working. Ideally I want the user to be able to customise their view by sorting the columns so in the interests of getting it working I've persisted the winning percentage value.

For this project the additional database isn't going to be particularly taxed but in the interest of learning there must be a grails solution to this. I'll post any solution if I find one, but if you've got a solution let me know. I'm off to cruise Nabble ...