Storing characters in stick tables

[Franks Andy (IT Technical Architecture Manager)]

Hi all,
  First of all happy new year!
I'm using haproxy 1.8 in case that's relevant. I've set up optional client 
certificate checking against a CA we have at the place I work, which is working 
really well; I decline access to certain uris based on whether the client has a 
certificate that matches certain properties.
I would like to store some of those properties, namely the common-name, 
preferably in a stick table, where I can simply pull off "stats" for that 
client within the stick table.
I'm already tracking connection rates etc, and am aware of the gpc counters, 
but can't find any reference to these supporting strings such as those from the 
certificate properties.
Doable?
Cheers
Andy