I would suggest that you do the choke tubes and the reasoning is that you may then use 'extended' chokes and by doing so will keep the constriction external to the bbls. My thot being only that I have seen several Belgian & German doubles that have been damaged in their choke areas [ringed] presumably by the use of steel shot.
And FWIW, my own pattern testing showed that you DO need choke for steel shot, or said another way the tightest patterns at 40 yards were produced using full chokes. That was with Remington, Federal & Winchester factory steel loads in shot sizes 3 & 4 and payloads up to 1.25 oz.
