Jackson Risner (Risener) was in Co. E of of the 1st Choctaw & Chickasaw Mtd Rifles (Cooper's Regiment and later Tandy Walker's). Jackson is on the roster of this regiment in July 1861.
There is no evidence I have seen that would suggest either were near Pea Ridge at the time of the battle. I am not aware of any documentation that would suggest any of Cooper's troops except Welch's Squadron and a couple of members of Cooper's staff were with Pike at Pea Ridge.
I have not seen the information provided by the Choctaw Nation other than what was included in your previous post. I would like to see the information either posted on the message board or you can email me at martikw@cherokeehistory.com.
I will continue to look for information on the location of Cooper's command at the time of the battle. It is conceivable that George Risner may have joined the 1st Choctaw after Pea Ridge -- that is, between March and June 1862 -- but at this time we don't have any evidence one way or the other.
I'm am putting a copy of the post on the Indian Territory message board as well with the hope that some of our researchers there can identify additional documentation on the subject. http://history-sites.com/cgi-bin/bbs53x/itcwmb/webbbs_config.pl?read=5242