I have the BDCW aux fan on mine and I installed the thermostatic fan switch for a trip to Italy last summer. It was 35 degrees plus much of the time and I too found the fans were on too much as I was riding a lot of steep, slow, twisty climbs. The problem was compounded as the second fan, unlike the OEM, has no shield to divert the hot air away from your leg. I was roasting enough as it was without having constant hot air being blown right at my thigh. I swapped the OEM switch back. I had to top up with coolant a couple of times but the bike never overheated.
Perhaps a thermoswitch that doesn't trick the bike into believing the temperature is quite so high would be a good idea Say 9 degrees up rather than 17 ?
2011 990 Adventure