I would recommend a steering bar not wider than 76 cm for road use.
Once I had fitted a Dragbar with 84 cm width and it was horrible.
To hold the outer end of the bar, while turning the bike, was difficult for me (height 170cm).
While riding at higher speed (100km/h+) the wind moved my clothing, my arms too and they moved the wide bar as well. Not a good feeling !
All the best,