Why not just use the covers as they are designed and take them off at night?
The whole reason they are easily removable is because the dark covers don't let the headlights shine through them.
The dark tinted covers aren't illegal to have on during the day, but they will get you a ticket (or worse) at night or when driving in conditions (rain, snow, fog) when your headlights are supposed to be on to make your vehicle visible to other drivers.
While it's commendable you want to achive enough light output for good visibility using other means, and without blinding other drivers, but that would be difficult to do without disabling the stock headlights and switching your primary lighting to be auxiliary headlights, which are quite expensive, and not the same thing as driving or fog lights.
The other possible solution if you're into custom things, is to find a similar vehicle they make the "blacked out" projector style headlights for (like the older Chevy fullsize trucks and SUVs), and adapt them to fit the Explorer. While not all of these items are "legal" in terms of being DOT and SAE approved, they'd be a much better and safer option than driving around at night with dark tinted covers over the stock headlights.