Mine was probably about 10 years old at this point. I used a clothes iron (flatiron) set on medium heat ("permanent press"), and a piece of "parchment paper" from the kitchen between iron and rubber. After 30 seconds or so, the glue was softened enough that I could lift off the rubber, a little at a time using a putty knife. It all came off in one piece, with essentially all the glue still attached to the rubber. My thanks to the person (forgot the name, it was on one of the "drive replacement" articles for one of the other model Time Capsules) who suggested the iron.
Skip, no idea whether the software would be happy with that size, but the specs I found for it say it's 1 inch thick which matches the 1 TB Toshiba drive I just pulled out of my unit. So mechanically it seems like it would fit.
I'm partway through this procedure -- the description is really clear and helpful. I used a suggestion in one of the other articles, to use an iron rather than a hair dryer. Works perfectly.
I noticed the vent holes on the three sides of the base are covered up by the rubber foot pad. That makes no sense. Scissors cut easily through the material, so now I have them exposed. I'm not sure how much difference that will make but clearly it can't hurt. Keeping hard drives cool is critical to their endurance.