I have a Nikon 500 f4 VR with a Really Right Stuff replacement lens plate. Does anyone know how well this will work on a Mongoose 3.5.
4th Generation (designer of the Mongoose) has a replacement foot that looks lower in profile, which I suspect keeps the load more centered for improved vibration damping.
I use a Canon 500 F4 on a Mongoose 3.5a and it works very well. I did replace the foot with 4th Gen version to provide better centering over the tripod as you mentioned. Because of the weight of camera and lens - be careful mounting and adjusting balance on the side mount.