I actually just bought 3 lengths to make sure one would work . They're very useful though so I will probably end up using the others for something else.
Thanks! Res adapters... hmm... I'm not sure exactly what you are talking about. My guess would be you are looking for the UN 120mm mounting brackets which can be found here:
Or here for a bit cheaper: http://www.sidewindercomputers.com/undezfor3gor.html