I think you might be right actually Luke. 8611 quoted as approx 18kg/cm at 6V and 15kg/cm at 4.8V. 15kg is the same as 8511 + there another guy claiming the 8511 is UK version of 8611 here (post 11):
http://www.rcuniverse.com/forum/m_11...tm.htm#1162634
So confusing.
Angus