Keeping dust out

Hi Everyone,
I need to pressurise the rear tub of my Hilux Dual Cab and was wondering if a small fan as used in caravan fridges and computers etc would do the job. The fan I have looked at is about 4inches diameter and delivers 72 cfm. I am interested if anyone else has tried something similar. I have no idea if 72 cfm is sufficient, but realise the tighter the compartment is sealed the better.

To this end I have an ARB canopy which is well sealed to the ute tub, and have foam around the tailgate to minimise leakage. The rear lift up door of the canopy is also well sealed. The Hilux tub has 2 water drain holes so there wont be much lost through these.

In the past I have had a flip up vent in the canopy which has been acceptable. Minimum dust most of the time, but occassionally huge amounts if on a slow track with a tail wind. The real issue is I have recently fitted a rooftop tent over the canopy mounted on ARB Racks, so the flip up vent will not operate effectivley now as the flip up is restricted and the airflow is changed by the rooftop tent and roof rack over the front cab, and I feel a fan pressurising will be a step forward anyway. However, it all needs to be compact, durable, minimal power usage etc and the fan I am seeking info about is all of these.

We use the vehicle for extended outback trips, Kimberleys, Canning SR, leaving soon for Googs Trackand on upto Darwin (Kakadu, Litchfield, Bungles etc) this year and Cape York next year, so whatever I do needs to work.

In my minds eye the fan appears to shift more air than what I imagine came in through the previous flip up vent at 30 or 40 kph, so it should be OK, but if there is someone out there who has been down this or a similar track (pardon the pun) I'd like to hear from you.
David, Albany WA