I've been freezing mine to save to make salsa later. I washed and dried them and just put them in a gallon zip lock. These are the smaller Improved Porters so I can fit a lot in a bag. I pulled a bag out last weekend to make a batch and let them thaw. I was thinking it's going to be a real PITA to shock boil and skin all these. Once they thawed the skins peeled right off. It was great. And they kept their flavor. I would say 75+% of the maters lost their firmness, but even the ones that stayed firm pilled very easily.
In closing. If you want your maters to stay firm and not skin easily don't do what I did lol.
John175® Will be my FIL or Step Daddy one day.