I have two FWSM in the lab. I was hoping to conduct some failover testing with these but it seems I have different licenses on them. One is a 50 context license and the other is a 20. I'm ok with temporarily downgrading the 50 context to a 20 to get the testing done but I don't know if that is even possible without purchasing the 20 context license. Is that something Cisco would help with? Does anyone have any experience with this scenario? Perhaps this is a better question for our Cisco SE, but I thought I would put it out here first.
You can only take the context license to 3 (the default) by clearing the activation-key on both of them.
I'd suggested saving a "sh ver" from both units before doing this.
You can do the failover testing with the default 3 context license in both units and once done you can copy and paste the activation key from the saved "sh ver".
If you absolutely need 20 context or any other number of contexts then your first of seeing your SE is your best bet.