The Swiss 1.5 F I tried worked quite well, but was heavy per volume, meaning the same volume taken up by 78gr. 3F GOEX, held 85gr. 1 1/2 Swiss (7gr. more weight). The Swiss gave lower velocity by 60 to 80fps.
I fed the particulars into the program, Bruce, and it was 300fps low of what the load actually produced in my 28" bl. 1876 .50/95.

My 14 bore ML rifle did 1,550fps with 165gr. (just over 6drams 2F GOEX) with a .682" ball of 482gr.
I've not shot it with 1.5F Swiss powder - yet.
When I input my 14 bore data with 1.5 Swiss, it showed, it showed very close to what I got using 165 2F GOEX.