It is the engine tie bar, yes.
It was my dads idea, his rally mini had one years ago.
when i said to him i was gonna by engine mounts he said, Nah dont bother, lets make a Tie bar and save £250.
So he had a ratch in the garage and found a Honda CB450 rear shocker mount ( he restores old motor bikes), we got some M10 threaded bar.
First off all we screwed a wooden dowel into the mount and made the mount to mount it to the strut brace. we measured up the angle they needed to be and then i got Mark to weld them on. We then figured out the angle the mount on the head needed tobe and adjusted that, Mark the strengthend it. A lick of paint and some rubber bushes and metal bush through the centre, we fitted it.
So now i have engine that is mounted on vibration free mounts and a rubber mounted tie bar with a small amount of flex in it, and i have to say it works very very well. No vibration, no more clutch judder and the car feels tighter.
we also made another bracket to hold intake pipe in place better, still rubber mounted, and we mount DV better and piped nicer.