has anybody got that?

if yes where on the gearbox did you install the tubes?

Taz implemented this for his 6-speed.

Is there any point/benefit in doing this?

Hook up a temperature gauge and see whats it's doing. Given they have only 2L of oil, it could be a good idea under harsh conditions.

IMO no
I have ran my 6 speed box for the last year with no issues including various 1/4 mile,track days and high speed runs.
For the cost of the box its not worth spending the money.

But it can be done easily.

How would the oil circulate through the cooler ? A pump ?

Yes a pump.
Via a cooler then back to the box.
Ideally a thermostat to control the flow would be needed as dont want it to run too cold.
The oil is very thick anyway so performs well under heatsoak

it is debatable, HOWEVER remember that my cooler setup uses a pressure tapping on the end of the box to directly lube the END bearing of the box that DOES go BLUE.

this is where the wear occurs, so when you launch the car, the load usually pushes the diff through the casing / the end of the gearset through the other end...

sure I've not done too many miles, but within 20 miles, the pump fires up ( I think i recall the temp is >80c )

you really want gearbox oil to stay at it's rated temp range, else it looses it's shear resistance / wear.

ALSO, OIL choice is very important.

HTH

normal road use is ok, but I'm not risking the aggro' on a 440hp setup

In my eyes a very good investment.
Again my look to OEM's.
My second job is engineer at ZF (gearbox manufacturer in Germany).
Meanwhile almost all gearboxes with high-torque- demands have oil- coolers additionally to their gearboxes.
Gearbox oil sometimes gets more than 140°C!!! We log temperatures, because we install ECU's within gearbox (sometimes swimming in the oil) and electronics will be damaged at temperatures >140°C...
Therefore we log temperature, that we have evidence at complaints.
I can tell you - 140°C is possbile and will be reached more times - and you won't need a track to get this. And I don't want to know the abrasion of gears or bearings in this temperature range, if oil is coming to its end!
And I am quite sure, that our gearbox will reach 140°C quite easily. Remember - Alfa installed a gear box cooler - at similar gear boxes, which handle lower torque than a tuned Fiat Coupe!
Juergen

Remember - Alfa installed a gear box cooler - at similar gear boxes, which handle lower torque than a tuned Fiat Coupe!

which model?

running an alfa 155 Q4 I want to cool the oil in the diff as well

celica gt4 has a gearbox oil cooler

So does my Rav 4, I know this because when I changed the clutch the oil cooler pipes broke.

Probably the same cooler as the GT4