I have found that you do not need a larger CFM "internal" fan since
the stock fan only comes on when the rig has a over temp condition or
while you TX.
What Icom has done by installing additional "Springs" in the mosfet
failure "fix" is to provide a conduction path for removing any
additional internal heat to the OUTSIDE case.
The addition of a small cooling fan on to the heat sink fins is all
that is needed as this will keep the fins cool and provide the needed
TOP and BOTTOM air flow over the case to assist the anti-oscillation
My 7K runs absolutely COOL with the small CPU style fan attached via
plastic screws to the heat sink fins, this while in extended RTTY and
FM modes, I built a "gender mender" that lets me use tha AH-4 and
provide the power to the fan.
With the fan removed the radio gets a bit toasty for my liking and
with the potential (according to Adam) of a 15-watt class A driver
stage I do not want to take any more chances with my 7k.