Too much guesswork here, even by rod, the question can't be answered realistically unless you know for certain what temps you are reaching, my old xr4i for example maintained a steady 130C at 55mph on a hot day, so had one, having heard how much noisier the cossie gets as the oil thins out, esp with castrol oil, I fitted one for peace of mind, with a stat, as like to keep nearer 80C - 90C.
The temps are likely to shoot through the roof on a cossie oil wise, the oil does at least as much cooling as the coolant don't forget, cruising should be ok but sudden big bootfulls is lots of extra heat to dissipate, gives the cooling system an easier time as well, and with a stat will always be ideal temp.
tabetha