Once you get to 100 grains, the incremental benefits of each additional grain becomes less and less, and may even drop. If your barrel is too short, not all the powder will burn inside the barrel anyway.
I used 95 gr of FFFg with my .490 patched round ball for years. When I went to in-lines with bullets, I started at 95 and worked up in 5 grain increments. I also used two 50 gr pellets (777) and three 50 grain pellets. I got the best results, both for shooting and for cleaning, with 110 gr of loose 777, under a 300 gr XTP. My only complaint with the loose is that it isn;t as easy to load a second shot in th efield, but I;ve always had plenty of time for that. There are decent reloading devices to let you carry loose loads ready to go.