Roger
That thing will fit under your BSA but having owned one I can report they're not the greatest.
I traded mine for a pre unit Triumph front mudguard number plate thingy
If space is an issue you could consider this 3/4 inch plywood box affair that I use.
Two sheets of ply cunningly cut to slot together when needed but easy to take apart and stow when not needed.
No screws used except the ones that attach the thin metal plate on the bench surface.
You do need a long ramp ( I use a piece of scaffold decking) to get the bike up there and an extra set of helping hands but it works a treat.
I saw the idea at
http://bbcracing.com/the-box/There are a few other wood type m/c lift ideas out there on the inter web
On the same topic a guy up the road uses an old hospital bed as a lift/bench
![eek *eek*](https://www.a7a10.net/forum/Smileys/default/icon_eek.gif)
The bed is fully automatic, raises and lowers at the push of a button, you can spin it around, lock out the wheels, sit on it while working. rated for 600 pounds apparently.
![smile *smile*](https://www.a7a10.net/forum/Smileys/default/icon_biggrin.gif)
S