You really need a gap of about 3mm between the guard and the radiator, this prevents fretting and provides better impact protection. With the guard mounted in contact with the radiator, the impact of a stone on the guard, will push the guard into the radiator. The gap allows a slight energy absorbing deflection without transmitting energy (and damage) to the radiator.
I agree with the gap. There is a gap between my fabricated screen and the S4RS oil cooler radiator since the top and botton edge portion of the screen is resting against the horizontal top plate and botton plate respectively. Between these two plates, the radiator fins are recessed. I push the center of the screen with my hand and there's play.
As for the water radiator, the screen is resting on the fins but I'm not too concerned with too much hard debris hitting since the front fender prevents most, if not all, of the kickup debris from the tire. The oil radiator is fully exposed to all road debris kicked up from the front tire. So far, 2607 miles later since the initial install, no issues and it's holding up pretty well. A few weeks ago, I've rode the bike on some dirt/gravel road for a good mile or so doing about 40mph and no problem.
edit: below is the pic of the screen as of today compared to the first initial install above.
