New and confused about the lighting

First off hello all and thank you for any help you can provide. Well my son asked for a bearded dragon for Christmas which has led me to you all. We will be getting him a baby and plan to use a 55 gallon acrylic we already had. We are trying to avoid mounting the lighting on the inside. The tank has two decent size cut outs on top. So bought a screen top to cover the holes and two double fixtures one over each cut out. The thought was this would provide some versatility... now the confusion starts. The thought was to use a 100w Powersun MVB at one end with additional low watt basking if the heat was needed. Then a CHE for night temps since we live in Michigan and maybe an incandescent in the other just for more natural lighting if the MVB filled the UVB requirements. There in lies the problem with the MVB not covering the whole tank we have been told us it's ok they only need access to the zone and not full coverage others say 75-80% coverage is a must. I could always use a powersun in both fixtures for overlapping coverage but wouldnt this be overkill? too hot maybe? Please any advise would be great it is almost christmas and want to have the set up running for a few days before to make sure all is good before bringing the little guy home. Trying to add pics below showing the tank and the cut outs.

Does the enclosure have an opening on the front? With just top entry it may be difficult to access for cleaning and maintenance, handling, etc. They tend to be afraid of approaching from overhead so try to avoid that as much as possible. The acrylic will intercept UVB so you'll need to keep your UVB light on the mesh or inside. The 100w PowerSun is good but I prefer using them as portable basking lights outside the tank and for travel. I prefer to use a T5 in the main enclosure so that you can set that at an appropriate height and then adjust heat independently as needed. This is an excellent option for UVB http://www.lightyourreptiles.com/22-t-5-ho-fixture-high-output-with-arcadia-d3-12-ho-bulb/ If you go with the PowerSun, set it at about 12'' (closer to 8-10'' when shining through a mesh top) above the main basking area. You could hang it on an adjustable lamp stand so it sits over the enclosure and you could possibly leave the mesh off if there aren't any other animals in the house. As far as coverage goes, you want a wide even spread of UVB over the basking area at least the length of your dragon to allow for even basking. A 24'' fixture covers most adult dragons so larger than that is appropriate mostly in larger enclosures.

For overnight heat, if the ambient temps stay above about 65 in the house then no additional heat is needed. Otherwise I suggest either a low wattage CHE (these get VERY hot and may melt the acrylic) or a heat projector (MegaRay and Arcadia make these) which run cooler to the touch. You don't want to add a lot of heat, just enough to bump the temps to the low 70s at most overnight. These can be used for supplemental heat during the day too.

Apprectiate the reply unfortunately no access in the front the only cut outs are in the top. I really wish UVB would penetrate the acrylic so I could place a T5 on top. Unless it is a must I really don't want to mount inside the tank but function over esthetics if it's a must. If I understood you right sounds like the Powersun would work as the area it produces will cover at least for now since we are getting him a baby. Also will place it on the right side above the branch on the screen and make sure highest point on branch is no closer than 12 inches to the screen/light. So as long as the UVB source will fully cover the reptile during basking it does not need to cover the tank? Seems to make more sense as I'm sure they are not in the sun all day and retreat to shade whew that's a relief. Thanks for the tip on the CHE's never used one so didn't know how hot they get going to make sure it emits no light also. Thank you again much appreciated.

The more variety in terms of temperature and UVB exposure you can provide, the better. They will move around to self regulate. I suggest with a 100w PowerSun to set it at around 12'' no mesh or 8-10'' through the mesh above the main basking area. Branches can offer slightly closer access. The 160w version can be more around 14-18'' or so. They will likely produce more heat though.

A CHE can get really hot. I dropped one by accident after taking it out of the fixture (via towel covered hand) and it instantly melted a bunch of rug. Ruined. I much prefer using the heat projector bulbs like this https://www.pangeareptile.com/store/arcadia-deep-heat-projector.html You can also hook them up to a thermostat to kick on and off as needed.