Some info on the 11th at www.geocities.com/Heartland/Hills/1850/11thvacav.html and
www.itd.nps.gov/cwss/ (search on regiments).
The Civil War Soldiers Sailors database (www.itd.nps.gov/cwss) did not list a George H. Robinson in the 11th, only an Amos Robinson. There were two George Robinson's listed from Virginia, but both were in Union units:
George Robinson, Loudon County Virginia Raiders, and
George W. Robinson, 1st Regt Va Inf (3 month volunteers, 1861).