Hi Kynoch - looking pretty good. Could be more powder, as in an 8 to 10 dram equivalence might give you the elevation and parallel shooting you are undoubtedly looking for.
Greener's #9th Edition shows 10 drams and on page 691:

"The 8 bore of Messrs. Holland, weighing 17 pounds 8 ozs., and fired with 10 drs.- a very light charge for this calibre, some of the more renowned elephant hunters using as much as 12 and 14 grs. this bore."

Note, these were rifled guns and heavier. Another weight listed from the chart page 689 lists:

Bore: .835", 10 drms., 862 bullet grains, 16 pounds weight of gun, 85.0 pounds recoil, mv 1,654fps, 100yds. 1,193fps, 150yds. 1,038fps - energy muzzle 5,232, 100yds. 2,720

Since a round ball .835gr. weight in pure lead is 875gr., we can assume the load listed above, the ball/bullet was an alloy/hardened, slightly.