Hello Basimpsn

The servos mentioned all have around 52 oz of tourqe and seem to do the job well. Im just not sure what the lower limit would be. The space available will dictate your choices on servos. I would use a metal gear if possible. PM me if you want to talk about it on the phone I would be happy to talk about the F-18, and give you whatever info you needed.

Dave use this link for the RDS, information and supplys.
http://www.proptwisters.org/rds2/index.html (RDS link)