The unit is well thought out and solid!! Since I've been using it don't use my full Wimberley much... use it for the 500 and 600 lens. The only down side (which I would not bother considering) is customer support, at times will take a while to get things done but they will ! Highly recommended !!!
Go to the 4th Generation Designs website http://stores.4gdphoto.com/-strse-HARDWARE-UPGRADES/Categories.bok Toward the bottom of the left hand side column is a heading called "HARDWARE UPDATES".
There are a couple of different options to upgrade a M-3 series Mongoose.
1. M-3 Ultimate Upgrade: replaces your previous model with the 3.6....$275
2. M-3 Great Upgrade: Reworks your existing mongoose with some of the technology of the M-3.6....$98
3. Standard Upgrade: Changes a couple of pieces.....$0.00.
Michael The flash bracket for the Mongoose is tiny and convenient, can't imagine using anything else !!!
Pao I use the Mongoose with the 600 which is heavier than the 800 !! If I don't have to walk a lot do prefer the full Wimberley, just easier changing converters, balancing and safer .. but the 3.6 will perform !!!