You didn't say which 90 gn bullet you are using, I used the Speer 90 gn hotcore for years in the 243 and killed one of the larger black bears I've shot with that load.
I might suggest to keep the 90 gnr and back off the powder a little. I did this with my son's 260 when we went to Africa a couple years ago (he was 9 at the time), loaded 100 gnrs down to 2800 fps almost 0 recoil and killed warthog and steinbok just fine.