The temp is on the high side, but is still in the realms of nature. The only problem I see with it is that if you have a temp spike your temp is already closer to a critical temp(84 to 88=4 degrees as apposed to 80 to 86=6 degrees which would be safer).
Covers just insulate the tank. If you have jumpers put some grating over the the top. I ended up getting the light defusing at Home Depot and putting it in a polyester mesh laundry bag to make the holes ever so small.
Also your temp can up all the way up to 90 without a problem. These fish arent mad of glass everyone. They're species been around for hundreds of years. Granted tehy wouldnt be comfortable, but they'll go to the bottom of the tank where is can be much cooler.
Turning your lights on later in the day will help out too. You can knock off a half hour here and there.