Thanks!
I've been keeping the cats out of there as much as possible and always do a head count at feeding time.
The tape and plastic didn't last, but I had some recollection of where screws were and was able to dry fit the cementboard-- although it was a pain. I still need to tweak it a bit. The adhesive is supposed to be 1/4" thick so that should make up for imperfections so long as they are less than that. I just dissected a rotisserie chicken and still have some grease on my fingers so my cat is licking them as I'm trying to type. LOL.
Current view:
Left side took two spacers to get 1/4" gap from tub. Right side took about 5 of them to be level. It's still off a hair but It shouldn't matter bc the top board will be cut off evenly, but I still had to raise up the edge so the board would actually fit. With it up I will be able to get shims in the right spots for the left board.
I managed to have my level fall down behind the board after I put one screw in and had to remove it and then get the level out. Felt like an idiot. LOL. Since I have so much aquadefense I'm thinking of coating the entire backside in it but that would take more time. I won't be able to do some parts until my friend is back and he'll have to get teeth pulled so I'm looking at week and a half to two weeks before he can help me again.
I'm debating whether or not to put plastic up if I do aquadefense. I probably will just in case-- IF I can get it up and it doesn't cause problems. I'm probably going to need pliers to get the spacers out from under that board. The stuff built up a little on the back on the edges (I couldn't see it when I was working on it) so I'll have to chisel that off to make the edges flat. The board was already bowing a bit in the middle from how it was propped up.
In addition to paint stirring sticks, I have popsicle stick type things from the craft section. They are thinner and can be used for shimming out. I can glue them to the paint sticks. I can also use composite shims, although they might be harder to cut and break than wooden ones, but that's ok. I can glue them all in place. That Titebond stuff works well once it dries.
I did take a chunk of 1x2 and tape part of a paint stirring stick to it and then cram it behind the board in one spot so I could run a screw through. I came in with a wood screw at the top of the scrap to secure it to the stud so it will stay put when I remove the cement board to clean it up some more.
Since it won't have tile or anything too heavy on it I'm not going to go crazy with the screws on top and bottom. I'll add a few more on the sides perhaps.
Thanks for the encouragement and suggestions.
Hmm.. I wonder if Mom has a hot glue gun. I can always ask her. I think she might.