Logically, It seems to me the correct place for the fan control switch should be as close as possible to both:
a) the engine thermostat, and b) the instrument temp gauge sensor.
Why so? Well for several reasons: Look at it from the point of view of fitting the fan stat in the bottom hose?
# If the radiator is good and efficient as your 4 core unit should be, then the output temperature out at the top hose could be quite high and get really well cooled before the fan ever cuts in at its preset temp setting.
# When the fan eventually cuts in, it will depend upon not only the efficiency of the radiator but also the ambient temperature and the speed of the vehicle - not the output temperature of the engine. That has got to be risky.
# If the ambient temperature was very high, the engine could be practically boiling before the temperature in the bottom hose was high enough (due to the efficient rad) before the cooling fan is engaged. Steam and over-pressurisation would then be on the cards.
# The temperature at the instrument gauge sender would never be stable, behaving like a fiddlers elbow, scaring the living daylights out of the driver with over-erratic temp readings.
# Equally the thermostat would be pretty much continually open (especially the 82 degree - low temperature unit) providing no meaningful stability over the engine temperature because the system output temperature would generally be above the stat closing point and the fan stat would be wholly dependent upon the normally much cooler bottom hose.
# Lastly the abilty of the system to control the output temperature when under heavy load or in slow traffic would be impaired, subject to the inevitable thermal delay whilst the hot water makes its way thro the rad before triggering the cooling fan.
Alternatively, mounting the cooling fan stat in the hottest part of the system (top hose) in close proximity to the engine stat and the gauge sender, makes much more sense and takes care of all the system problems outlined above.
Finally, although its a preferential issue, I personally think the RV8 functions more efficiently in the 90 to 95 degree range than it does in the
85 to 90 degree range, making the 88 degree stat a better choice for temperate climates.
My reason for this conclusion comes from running Efi V8's for 17 years and learning from the Rover Efi tech training manual that the optimum temperature for the CTS is around 95 degrees C. when the ECU delivers its most efficient (power and economy) mixture.
! Although I'm always open to advice and opinions 
