I just used clear packing tape. hasn't shown any signs of melting in the printer or anything so I think it's pretty safe.
I agree, that board came out very good. I am very happy with press-n-peel... it's good to find a product that works like it's supposed to... or even better
as for my etching method, I take 1/4 cup of water, and microwave it until it's boiling, and put it in a ziplock freezer bag (I use freezer bags because they're extra tough)
and then I spoon in 3 or 4 teaspoons of sodium persulphate, and shake until dissolved.
then I put in the boards, carefully force out as much air as possible, and seal the bag. then i can hold the bag in my hands as I etch, which allows me to agitate it by hand to make sure it etches quickly and evenly. it's also REALLY easy to see the progress of the board, as you can see in the pictures...
and it only uses a very small amount of etchant at a time, so it's not wasteful. sodium persulphate turns blue (like windex) as it etches, so when it gets very blue it's time to replace it. I can usually get 3 or 4 boards in a baggie of etching solution... and when it's time to clean up... i just have to dump the solution down the toilet, and throw away the bag. doesn't get much easier than that!