Welcome to the Campfire 577, you will be fine with your Gibbs bedded the way you mention, I don't believe pillar bedding is necessary, especially with the cross bolts doing the anti-splitting duty.
For what it's worth, I had the same concerns a few years ago with my Gibbs, I purposefully and with new Jamison cases loaded 50 rounds with the 600 gr Woodleigh protected point bullets to a full 2450 fps with H-4831 powder to check the relation of my stock and crossbolts to the barreled action, all turned out well.
I then proceeded to load the remaining 50 sticks of brass to a more sedate, yet believe to be equally as effective 2150 fps with the same 600 gr Woodleigh bullets, also have a 600 gr solid load now to go with the soft.
Good Luck, and hang on, she bucks a little.