Can it be mounted on a dorade box?
I think it's no problem if the box is large enough. Removing them is easier if you use a flat head
screw driver to tap from the bottom rather than prying from the top. Either way this is a slow is pro job. The plastic is hard and breaks if not patient.
I'm not sure what you hope to avoid using the dorade box other than an extra hole. Cutting a large hole in a small piece of material leaves it very thin at the margins and subject to breakage. Crew members step on the dorade boxes. The other issue with dorades is depending on the orientation they exhaust
or they supply air. The Nicro fans can be set up either way but you might need a switch to reverse them since they won't be accessible from inside the dorade. The dorade orientation has to match the rotation direction of the fan. Should the two be opposing you will divert the flow from the dorade. It can be a power boost to the dorade or the opposite. With a good breeze the dorade really won't need the fan.
Where you place them and how you use the exhaust
or supply feature is more the key. You want to establish good air flow so that as temperatures and humidity changes you can exhaust moist air made up from outside dry air. In the head
is a good place since the shower
makes moisture quickly. If running air conditioning
you are fighting yourself. You do need to set up a procedure how to configure the dorades and fans based on the situation.