The billet cool seems to to a really good job for my type of riding. 90% of my riding is on the road. I have seen as much as a 30 degree and more drop in oil temp. I usually don't take the cover off until the temperature gets over 90 degrees. The cooler has about 14 fins that are approx 3/4 of an inch deep and the oil passes through twice. I like it because it is simple and it has no hoses or clamps. I do like the fact that it does set the oil filter out a little further. Why buy a chrome filter and hide it. It does make oil changes a lot less messy. I use a half gallon milk jug that I cut the top portion out and just slide it in under the cooler. I was concerned that there would be cooler spin off when removing the oil filter but when you install it you just clean the filter nipple and all other parts real good with alcohol and use blue locktite.

The web site is:
http://www.billetcool.com/oil_cooler.htm

 

After reading the istructions, it seems this could be in supplement to the existing oil cooler. Doesn't appear that there has been any updates since 2006 model year. Correct me if I am wrong, but isn't the same oil filter used for 88,96, 103 and 110 motors? I don't think there is an oil filter change since 99 on the twin cams, right?
Seems like this would be usable on newer than 06 engines.

 

I have the billet cool on an 08 Deluxe. They are a mom & pop operation out of some where in Colorado. I cant' speak for filter placement or specifications on all models or model years but they were more than helpful when I called them. As for running it in conjunction with another cooler I would wonder about the other coolers adaptor and fitment.