If you can get metal lath, that is what I would use.
Redgard is not needed on the preslope.
1/2" is fine for the curb on the sides. 1" for the top.
Redgarding the studs? NO. That would be anticpating a leak. The niche needs to have cbu all around, taped and Redgarded.
1 gallon should do the job.
Here's some info: http://www.ontariotile.com/preslope.html
Work is for those who can not fish.
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