I know this has been discussed here before but I’m still having a hard time. I’m installing the American Standard Studio alcove tub with an apron. What’s throwing me off are the 2 rails running down the length of the tub. Do I want to put the mortar in piles in between these rails to support the osb underbelly or do I lay a thin layer for supporting the 2 rails? If I put mortar down the center, the rails won’t be touching the floor and I have to be careful not to use too much mortar because it will just get trapped between the rails. My understanding of the manufacturer’s instructions are to make sure the rails are supported but it’s not really clear. They provide video install instructions but they don’t even use a mortar bed.