pbekkerh wrote:

In traffic temp rises fast

A thermostat will only make this worse, as any thermostat will decrease the opening somewhat, even at fully open.
It can only help raising the temp on cold days, by lowering the flow to the radiator, it can't increase the flow, over what is possible without it !

Not always true. On some engines having a restriction can aid cooling by allowing more time for the coolant to absorb heat. Instead of rushing quickly past without taking the maximum amount of heat possible. Can supposedly maintain a more uniform temperature over the complete cylinder too.
On my MC21 race bike I just took the centre part of the thermostat out, leaving the original orifice as it was. I haven`t had any problems with the temperature yet. (Touch wood)!