May I ask what kind of camera you are going to use and type of lenses to attach?
I have experience using the Letus and the PSTechnik adapters in our studio, both give very good results but has about 1 stop light loss or more. Both setups are quite heavy as well. Also, Letus (or similar Brevis) setup tends to "shake" when used while moving, so it takes practice (I stick to using the adapters on a tripod.)