Bigger Radiator - Any Experiences?

Never heard of an issue requiring a bigger rad. If its not actually overheating then there isn't a problem. The fan may be cutting in frequently but that's what it's there for.
If you're intent on a bigger rad, logic would suggest one from a 1200 but they seem to have the same part number, as do the thermostat and fan so maybe not.

 

As @Pegscraper said, the fan coming on and off is simply doing it's job.
If you feel the temperature is getting excessive, then there are a number of ways to up the coolant quantity, however I would first prove your thoughts running a calibrated thermocouple (cjc) to ensure there is actually a problem. A cheap type J should be adequate.

If there is an issue, then you may want to consider the viscosity of the engine oil used. A 10w50 oil performs better than a 10w40 over 100⁰C

 

@Trierer Don't know about over there but here you can get oil additives that help cooling a lot.

 

Been running Castrol Power 10W50 per rec of Triumph Dealer in my Bonne; fan rarely comes on; no issues.

 

In reality, choice of oil brand or grade will make minimal difference to running temperature on a liquid cooled engine IMO. If an engine is prone to overheating it certainly won’t prevent it.
I’ve used numerous additives over the years, many with claims of increased power, engine smoothness and longevity but now just stick with the MO of using a quality oil, of the manufacturers specified grade and change it regularly, adjusting change intervals to suit type of use and riding style if required.

 

I wasn't suggesting magical cooling powers of the oil @Pegscraper but providing better lubricating properties at elevated temperatures if they are inevitable to minimise wear.

On a separate note @Trierer I fitted YSS gas rear shocks and it made the rear suspension far superior to OE. Mine is mainly used two up and the originals were far too weak for spirited riding.