I was tempted to get the large one first...but I want to test a small one.

Thank you for your reply. Could you describe your heating pad setup? Or a pic?

I use my phone for internet these days, and it hasn't been letting me upload pictures. I have a larger one, big enough to cover the entire bottom of a ten gallon aquarium. It's laying on a table top with a dishtowel over it, and kind of crowded with plants in nursery pots, no bigger than 4". I take them off to water and let them drain well in the sink before replacing, and mist lightly on the pad. I talked to several growers before setting it up this way and this was their advice. Eventually I'd like one with a thermostat, for now just keeping a close eye on it. In a week or so the Hoyas should be rooted enough to remove, I plan on keeping my Sans on it all winter along with a rooted Hoya kanyakumariana, since that last one likes to be warm. Might switch to a smaller pad at that point.

Honestly, my opinion on size would be to go for a bigger one if you can, since they don't cost much more than a smaller one. I think you will like it once you try it!

Do you have the sticky side on the table?

Sticky side up, with backing still on. No problems yet, but out of paranoia I check it often just to make sure. Later I am going to pick up some unglazed terra cotta tiles to put on top to distribute heat. When I worked for a herpetologist, this is how we set up reptile cages. Worked well.

Thanks for the info. I read elsewhere that someone was using aluminum foil on the sticky side. I wonder if that's safe.

I'd be more inclined to use either a piece of glass or tile than something so conductive, but that's just me.