from
http://www.uvguide.co.uk/uvinnature.htm
It can be seen that during most of the day in their natural range the microW UVB /sqcm is higher than 300. Peaking at just under 500 microW UVB / sqcm . I've lived in CBD territory and seen them out ( hunting, foraging , basking) right through the day except on the very hottest days (can reach 50oC there).
There are no commercial UV tubes or globes available designed for reptiles which will produce the levels of UVB beardies encounter in their natural range in summer , the UVB source would have to sitting on the beardie's head or back to reach UVB fluxes higher than 300 microW / sqcm.
It's unlikely to that you can mount your UVB source (compact, T8 or even T5HO) too close.
An MVB will literally cook the beardie before you get close enough to have even 300 microW UVB / sqcm.
Think if you try to get about 180 - 200 microW UVB / sqcm at the basking spot you will be doing OK.
About 200 microW UVB / sq.cm corresponds to mid morning & mid afternoon in their natural range in summer.
A good guide is shown below :
If she likes to bask where she is in the photo, she's obviously not too hot there .
How far is her basking spot from the bottom surface of your MVB ? .... Might not be sufficient UVA and UVB where she basks (is very tricky getting a good balance between heat & UVA & UVB from one source..
Here is some data for an 80W MVB from Arcadia.
The optimal distance shown between the lines is determined by temperature.
If you are already getting 40-43 degCelsius at the basking spot with your current MVB, going up to a higher wattage MVB will not help .
She can do with a T5HO 10% - 12% UVB tube mounted in a reflector hood which is mounted UNDER the mesh lid and with one end as close as you can manage to the MVB. This way you can produce both a nice thermal gradient and a nice UVA and UVB gradient too.