this works! There is a little slip as the munter knot turns over but the amsteel line is so small that the slip is almost not noticeable. And it unties easily if you use a slip knot.
This Amsteel is stronger, lighter ( and softer - not sure why that would matter?) and with the munter mule I only need one ring!
There is someone else on here that uses the Garda Hitch (can't remember who), anyway whoever you are - check out the munter mule - only need one ring and it seems to work ok on slippery lines.