It's not as simple as "any beam axle is wide open."

The rear axle of an Golf/Jetta is literally an antiroll bar, by the definition in the GCR and in its function. Further, there's a specific provision in that definition that recognizes that an ARB can serve other functions - specifically, that it may locate the suspension. ARBs may be added, modified, or removed/replaced...

ERGO, that thing on the back of my Golf is free game - as long as it mounts in the stock chassis pick-up points and bolts to the stock stub axles, etc. I figure it would cost me a couple grand to make it happen - not counting someone actually doing some engineering math to help make sure it doesn't break in half.

Now, if it were a straight axle like on the back of an Audi, located by arms, the same allowance wouldn't apply.

K