Your GE 7-28800 radio looks like a thinner, smaller radio than a Superadio. It's hard to tell how large the case is with the picture I saw on EBay.
The best way to find out how big the loopstick is, is to open up the radio and look and measure it.
But a long loopstick isn't everything.
My Panasonic RFB45 is a better performer on MW than my SR radios and it has a smaller loopstick. I've never opened up the radio to see how big it is, but it's probably 140mm or so judging from the size of the radio's case. I also have vintage transistor radios with 180mm and 200mm loopsticks that suck on MW. So the antenna is obviously important, but it's not everything.