Take a 600 square foot home with 8 foot ceilings, something perhaps
that could have a space sensible gain of 10,000 Btu/hr when you exclude
infiltration.

You have a volume of 4800 cubic feet.

Now considering this is a low building and the fact that it is not
winter, there will be no 'stack effect' caused infiltration to worry
about. It is not a multi-floor building so I would also doubt there
would be any sort of any inverted stack causing increased infiltration,
so for the most part be some wind driven infiltration.

So let's see what significant natural air leakage is, in the summer. If
you had something perhaps 2 air changes per hour in the winter due to
infiltration, then perhaps that could be considered very poor. So with
just some wind effect, from a slower, less dense summer wind compared
to a faster more dense winter wind, I will give you the benefit of the
doubt and say it could be one air change per hour.

So to look at this infiltration on a per minute basis, 4800 cubic
feet/60 minutes is approximately 80 CFM.

You have a scheme that could pressurize a home with 1360 CFM or perhaps
exhaust 1360 CFM. Or minimize things and have 617 CFM pressurization or
perhaps 660 CFM exhaust. Do you really think that 80 CFM of
infiltration is additive to this mechanical exchange? Ultimately a
natural pressure differential drives the natural exchange, in this case
there will be a mechanical differential. Maybe consider the
differential pressure required for 80 CFM of natural infiltration vs
1360 or 660 CFM of exhaust.

Hey argue that it is a super insultated 2000 square foot structure then
that has the envelope integrity of swiss cheese( never see this,
someone going to the extent to super insulate would pay some attention
to air tightness).

2000x8/60= 267 CFM infiltration from natural effects, The exhaust fan
or the outdoor evap cooler are still going to be able to over power
this even with the air flow rates established for a mere 10,000 Btu/hr
sensible gain.

Infiltration will only come into play when the system is cycled off or
perhaps some severe weather moved in like a hurricane.

Try the Florida Solar Energy Center link I gave you, go down and see
what they say about a 2 Pa pressure differential. They are fellow solar
geeks, maybe you will believe it if you hear it from them.

I pressurize to prevent humid air with a 79 to 81 dewpoint from
infiltrating in so what do I know.

I think if you thought about the pressure differentials you would not
be pressurizing the garage or attic while depressurizing the home at
the same time. So there is another piece of the puzzle for you.