Not me - you might try another forum?
Are you planning to use wallplate elbows (the things used for outside taps)? It's common to use them mounted on a batten between the studs, rather than expecting the wall material to support the valve.
Just put a noggin in assuming you are using 3X2 or CLS but turn it through 90º so that you have a solid mount 1" inside your wall for your shower. Notch a bit out if you need it any deeper.
Never heard of wedi board before but I looked it up here and I'm inclined to agree thats its worth a dabble.
If you want to make doubly sure of its strength, use a back board in the stud wall, and supplement it by using different fixings to those supplied with the shower.
I'm about to do something very similar to you, and the shower comes with standard screws and wall plugs. However, I'm hoping to use hollow wall anchors instead of wall plugs.
In case you're unfamiliar, they're clever little fellas which screw into hollow wall, and upon tightening have arms which fold back and brace the inside of the wall.
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