Hopefully someone can chime in who has more Brian May knowledge than me.
i do not think of massive reverb when I hear Brian May, probably a "Room" reverb would be most suitable as that is more of a "You don't miss it till you turn it off" reverb, it can get quite subtle… But you can probably tame Hall quite a bit to be like that.
which Space algorithms do you have on your H9? I might be able to point you in the direction of a preset…. Then we can try and help you tweak it to your taste