Howdy Mr. BrownBear,
Having never hunted Kodiak Brown Bear, I do not feel qualified to offer an opinion regarding the use of a muzzleloader in pursuit of same.
For the benefit of others who may not have hunted here in Alaska, may I respectfully offer the following:
An Interior Grizzly would be considered quite respectable at 7 foot and an 8 footer is a large Bear and considered quite an accomplishment to obtain.
Those who have not had the opportunity to observe the difference in size (mass) between a 7' and 8' Interior Bear, might be quite surprised imho. Same goes for Kodiaks, 8' as compared to a 10 footer.
As an observation, I would like to state that what our Bears may lack in overall size, they make up for in general orneriness and aggressive belligerence. (Heh, heh, heh.) Never to be taken lightly.
Am certain you probably feel the same way about your Brown Bears (Only probably even more so?).
Thank you for sharing your insight, for the benefit of all.
Best Wishes