Sorry to put a downer on it but can't personally see it as a very effective tool for regular training. Hanging two hands facing each other isn't very climbing specific and personally I don't it would be as effective as the standard face on fingerboard position. Havnt tried it for one armed hangs so obviously cant comment but wonder what it's like stability wise? Does it roll at all if using it just one side?
Its what I've been using for the last few weeks for my weighted hangs with superb results and before that on a prototype for a 90 hang workout which included alternated finger combinations, repeaters, encores and maximal hangs.
Before that I also did assisted one armers on an edge with foot in an etrier on a pulley and counterweight set up which gave enough stability.
However, I agree for unassisted one arm hangs and pull-ups on the smaller slots it will be
If you think about it in one handed work on a fixed board you would tend towards the same side-on position as you would hanging on the Wedge with two hands.