This is a link to my full review of the Manfrotto 293 Telephoto Lens Support Bracket. It discusses how it can be used with the combination of the Olympus 70-300mm lens plus EC-14 teleconverter. The review also includes a section on how to modify the bracket for use with shorter lenses, such as the 70-300 alone.
You can read the full review at:
Attached are 3 shots, one of the bracket and 2 of it in use.