Never done an SX4, I’m assuming it’s aluminum is probably why they aren’t recommending it be D&T, that and they don’t offer it I assume.
But I have done a ton of 870s, 500s, some Benellis, and Berettas. No problems if done correctly like any other D&T job.
I would insist that whoever does it does so on a Milling machine, only one chance to get it right so not the place for a drill press IMO. Probably calls for 8/40 screws and a dab of Loctite on each.