Here's a cautionary tale. While I am waiting for my new heater block my old heater element has no home. (The thermocouple broke off, so that's no problem.) Fortunately the unused feed tube on top close enough and just the right side for the heater element to sit in. As long as I don't accidentally heat up the right heater element there shouldn't be any problem.
Fortunatly the only damage was to the grabbing mechanism which pinches the feed tube into the feed hole, which I haven't been using this week since I switched to a top-loading option. But it could have been much worse.