Hi Randy,
I use 1 part Portland cement, 1-1/2 parts Perlite and 1-1/2 parts Peat. I use the Ziplock sandwich bags so I don't know if they're thicker than other ones or not. The amount of tufa I put in the bags is maybe about 3/4 full so I can fold the top of the baggie down toward the inside of the pot when firming up the sides. I'll make one this weekend and take some pictures to post.
Fun to get your sister hooked!! I'm working on my sister too, I've already succeeded with my Mom.
