You should not modify the perftune_Solaris.xml file. That file already has performance tuning options that were tested to work.
If you want to play with those options, then copy the template to a new template name. Unfortunately, we have not tested this server class, so it's up to you to find the parameters which work the best in your environment. If it were me, I'd start with the perftune_Solaris template, then slowly increase the thread counts given the number of CPUs you have.