Jim, your numbers got me a little curious so I did my own test. I also used 1.5 swiss but its kind of old so the numbers may be off a little. A jamison case weighs 220.4 and hold 95.4 gr to the top of the mouth. A BACO 348 case weighs 215.8 gr and holds 99.6 gr to the top of the mouth of the case.
I don't have a Shiloh chamber drawing but do have the standard reamer print from PT&D. I have attached it as a pdf. While not exactly what your looking for, its something to look at and ponder.
Sam