I am assuming that Clam uses a common swivel mount ...Otter appears to use the same swivel mount as well . If the arms attach to these then you should be able to achieve instillation . I could not find any video/instruction manual for the Clam arm rest ..May be Email Clam ...they may give you a heads up on the manual and/or Otter instillation.
file:///C:/Users/tom/Downloads/Otter-Pro-XT-Lodge-08-17-15.pdf