What I have found is that my wife's heritage softail runs hotter than my road king. On a summer day the oil temps in the summer run 230-240 whilst my road king is 220-230. My '17 road king has the added fan assist which cuts off between 35-40 mph, so is for lowers speeds and especially traffic. Her JAGG cooler is simply thermostat controlled, but once again no advantage at speed. I just installed her Jagg set-up so we will see this summer about the temps in the sump.
Since I have only tested my M3W this winter the fan never kicked in on the cooler, but the oil got warm enough to bypass to the cooler.
The cooler is 4-5 or so inches deep, but you also need to have space for the oil lines to come out the back. the choice was either lower and under the engine (which I did) or forward and in front.
I also toyed with the idea of mounting it under the bonnet. No air-flow from driving, but when the fan kicks on that is not an issue. Of course that would also mean oil flowing to the cooler whether it is hot or cold.
The other down side of cold oil to the cooler is that the cooler is 3/8 ID versus the 1/2 ID. 1/2 ID has 50% more capacity over 3/8 ID (2rPI). As I also mentioned the fan cooling the jugs is essential especially the bigger the V-twin becomes.
There is an often heated debate (pun intended) on whether one should cool the oil or cool the jugs. I think the answer is "yes".

Last edited by rcmatt; 20/02/19 03:35 PM.
Rodger
2018 M3W "Dreamers on the Rise"
2004 Plus 8 (wife's)
old Goldwings and a couple of Harleys