I sometimes use a 35 degree grid with an 11.5 inch reflector. If you have the 7-inch universal grid set (I have one and am familiar with that one from Adorama), the 10- and 20-degree grids are pretty small sources of light, yes.
And agreed...with a grid, there is NOT much light at all to reflect...
I'd be tempted to use the 20-degree grid AND just that, and then use a weak fill light from the second light...you'll still get a grid-type effect, but the shadows will have some fill.
Depends what you want to do, what your goal is...like the woman with the hat shot....LOVE the hat, love the topless with suit jacket ample cleavage look...that's not really much of an area that needs to be lighted up, so the 20 degree grid from maybe 12 feet would make a great "pool of light" look...but if you want to have some detail in dark clothing in B&W, you'll need to have light in some of those darker areas. I think what's going on is this is early days...you're finding out "how" these lights work with those modifiers...at those distances. I think you're just not used to how FAST the light drops right off the cliff and into full-blown, black, detail-less shadows....your EYES can see into the shadows, but the camera sensor is rendering the dark areas BLACK. I think your eyes are seeing the modeling light and any ambient light in the room, and the FLASH exposure is wayyyyyyyyyyyyyyyyy brighter than the ambient that you are seeing. Try squinting till your eyes are almost closed, and that will simulate the dynamic range you'll get with a proper highlight exposure. Again, I think this is your eyes being able to see into the dark zones due to ambient, but the FLASH exposure is not the light your eyes are seeing.
If you need more fill...you could try dragging the shutter at 1/4 to 1/6 second, and maybe pick up some of the modeling lamps' light, especially if converting to B&W. But it would be easier just to get more light into the shadows, and stop worrying about a specific hair light if you only have 2 lights.