High output headphones

I'm looking for headphone/earphone suggestions. I am trying to present speech to persons with severe to profound hearing losses (poorest thresholds of 90 dB HL). I have tried etymotics ER4s and their ER3A insert phones along with Shure E5 in ear monitors and Sennheiser HDA200 headphones. All start clipping the speech before I can achieve the desired real ear output. I am hoping to match the real ear outputs suggested by a prescriptive hearing aid fitting formula (DSLi/o). This results in rms levels for a speech noise, shaped to match a flat 90 dB hearing loss, of ~125 dB in a Zwislocki coupler. When I present my speech at this circuit setting the peaks are quite clipped.

Does anyone have experience/suggestions for other earphones to try? I'm afraid I can't use custom devices due to the number of subjects I'll be running so I need something with reusable/replaceable tips or cushions.