I need some expert/experienced advice on my shower tile install.

I have a solid surface shower pan that I roughed in as per spec. The inside surface of the flange sits exactly 1/2-inch proud of the framing around the pan. My plan is to use 1/2-inch cement board over waterproof membrane of some sort (tar paper? Polyethylene?).

My question is this. How do I detail the membrane where it meets the shower pan? The manufacturer (Swanstone) recommends attaching it to the framing and have it overlap the flange on the pan. Sounds logical, but it seems this will be the weak link in the install. The flange is only about an inch high, and is right where the splashing will be most severe. I would think this overlap is minimal. Should I adhere the membrane to the shower pan somehow? I assume the tiles will overlap this joint. But by how much? Doesn’t there need to be a gap under the tile? And I wouldn’t think thin-set will adhere to the membrane that well anyway. The manufacturer says to caulk the joint at the bottom of the tile with silicon sealant. But I thought the whole idea of the membrane overlapping is to keep any water that makes it past the tile/backer-board, and redirect it back to the pan. Won’t the sealant try to hold it back?

In retrospect, I wish I had ignored the install rough-in specs, and let in the pan into the framing. But it is really too late for that now as I cannot fir out the entire wall to meet the flange (one side of the shower is coplanar with an outside wall).

I have Michael Byrne’s excellent book called Setting Tile by Taunton Press, but nothing I find is specific enough as to this meeting of tile, backer-board, membrane and SS shower pan. I have limited tile experience (obviously), so any and all help is appreciated.