I haven't shortened my flat bar, but that is a valid point as there is no space for a light with the aero bar clamped to the flat bar. I put the light on the nose of the aero bar, plus then it's not shadowed by anything in front of it. I carry a light with rubbery strap attachment, usually lives in my trunk bag. Before getting that, I also have a big flamethrower of a light, two beam with separate big battery, the light clamps same on the nose of the aero, and the battery can velcro to the aft part of the aero or go into my jacket pocket.

My bell is on the right front of the aero, mid-cable brake lever is on the left front of the aero.

But for lights or bell, if no aero bar, those can also mount to the handlepost or vertical section of a conventional stem. I did that with the bell on my road bike. A light, need not be immediately at hand, can also attach to the top deck or sides of a front rack.