The standard Tiger expansion tank bracket has a flat piece of metal, sort of like a foot, which I believe originally would be bolted through the chassis rail at the front of the battery tray. Like a number of people I wanted to mount the tank further back (uses spare space in front of the scuttle and allows more access room around the back of the engine). The lower foot was cut off and the horizontal piece of metal was used to bolt the bracket to the battery tray. However, this has no fore/aft strength, i.e. if somebody leaned on the expansion tank it would bend the battery tray aluminium. To get around this I cut a couple of 'legs' from 20mm wide steel strip.
When mounting the bracket I bolted down through the bracket, then the battery tray and finally the legs (one on each side). The end result is pretty sturdy.
Engine coolant plumbing complete.