Hope you don't mind, opposite of stomp...
I have seen and handled the #58, it is awesome.
Looks like the 45/46/50, but with longer top rail, obviously,and an alloy extension, bridging the distance, the shorter lower handguard, doesnt reach. Nicest of the SIRS, IMHO. When the pics of these are available they'll be all over the place and they're going to be flying out of your door.
If you've got a middie, run for one of these...you'll see.