1. From JimZ's: http://www.spacemodeling.org/jimz/centuri/cen5037.txt
2. From the Semroc website: http://www.semroc.com/Store/scripts...arts.asp?ID=570
3. From YORP: http://www.oldrocketplans.com/centu...-9/Cen_KA-9.pdf
Header card says .908" dia. That would be an ST-8. And the motor tube would be an ST-7.