I taped an old Bandai 1/48 Jeep together and took a couple of pics with the chassis of a 1/56 Company B SAS Jeep for comparison. You can easily see why I, personally, wouldn't even consider using 1/48 models with 28mm minis. They are just too big and, the larger the vehicle, the bigger the discrepancy will be.
Please excuse the photo quality. I'm still trying to come to terms with a new camera. (Looks like I didn't tighten the tape enough, either. You'll get the idea, though.)