I have fitted Autocom, Cardo and Interphone speakers and mikes into my Shoei Multitech and the wife's Shoei xr1000 with no problem. Neither of us know they are there comfort wise.
I put a small bit of Velcro inside the ear recess of the helmet, although the Velcro is as much on the end of the chin strap as in the recess and just push the speaker on in as about the nearest place I can. Cables get tucked under the cheek pads lining and pushed up between shell and polystyrene as much as I can. If necessary I use some duck tape to hold in place.
Good luck. Persist with it for a while.