A photo always helps

This is the row already installed.  The fixture in question will be a couple of tiles closer to the camera. 

Eyeball Trim

I second Ron's suggestion. Depending on just how high the fixture is above the head of the operator, you might still get some shadow and you might still get some brighter and higher area on the backdrop because the eyeball is aiming more of the light toward the backdrop, but it is probably the best compromise.

Alternate suggestion: Place (hang?) a sheet of cardboard or paper or a sheet-sheet 10" closer to one of he lights you already have and see if you get a significantly brighter area than on the adjacent backdrop/wall location. If so, you can also try the lower wattage lamp you are considering to see if that helps.

Dante

Running contrary here

As a person without a home layout, I'd go and take the contrary view here and say you might be using the wrong lighting method here. The object of light placement for a layout (IMO) is to avoid the creation of shadows as much as possible and as such placing the operator between the layout and light source is far from ideal. So I'd use that style of lights you installed to just light the isles of a layout for operators to see where they are walking. I would use LED lights/LED strips instead placed behind a valance to light the deck and backdrop directly below it. This way you never have shadows of operators on your layout unless they reach in to uncouple a cut of cars or re-rail derailed cars/motive power.

Thanks...

I think I'll give the eyeball trim a try.  I hadn't thought of that, thanks for the suggestion.  I can always move the fixture later if it doesn't work out.   

Randy