I purchased one for my 14WG and spread it out on the bench for a test fitting and noticed lots of parts. Theres an inner circular piece that is mounted to the face of the throttle body via standoffs, then the filter is mounted to the circular piece. It seemed like there should be a better way to do this. Once I got the old A/C opened up and saw the breather oil in there, I knew I would be modding that as well.
I set the circular disk and standoffs aside and drilled a hole on each side and installed some thru-bolts and nyloks.
For the breather issue, I drilled a hole in the backplate and ran some hose up under the tank, and down the spine, exiting underneath. Sealed up the holes and stuck a fork in it...

 

Just a thought on how you set up your external breather; I've experimented with multiple different external breather configurations and have found that the shorter the hose runs to atmosphere, the better.

The engine is hot enough to keep the crankcase gasses as a vapor, when they exit the engine they begin to cool and the oil will condense back out. Running the hoses up over the engine and down to the ground as you have I'd expect you'll have oil in the hoses and dripping from your hose termination point fairly quickly.

It's a smart idea not to feed that hot, oily, oxygen depleted gas back in to the A/C but if you can get it to exit the external breather before it cools and condenses back from vapor it's even more efficient and cleaner; keep your hose run short, hot, and low...

This it the cleanest setup I've ever used, the gasses are still vapor when they hit the filter and are exhausted...

 

I agree with the theory, but it just hasnt been a reality in my life. I ran your rig on my 06 Sporty for a while and got tired of cleaning the oil off the ride side of the bike. I even had a dedicated pair of jeans that I wore due to the right leg being stained. The amount of oil I found in the aircleaner told be that not all of oils in a gaseous state.. The WG isnt any different. The breather passages from the head to the aircleaner are only an inch or two long. This was just step one. I plan on fabbing a catch can so that it doesnt end up on the road or tire. Maybe its the Az heat!

 

It could also just be my specific 103"; I've had a problem with this bike and excessive oil carryover from day one brand new. I'm methodical with my oil level yet it has always vented more oil than any other HD I've owned. I bought some Trask Mystfree breathers to replace the stock HD setup and I'll be opening the oil drain holes in the rocker plate when I install them this winter hoping to minimize the venting.

A catch can is a good idea, when I had my drain hose run under the bike I was getting oil splatters even using a push on filter; so far this under A/C setup is working well, but if it starts drooling oil I'm going to grab the chrome catch can DK Custom now has on their website and mount it under the A/C... desire walks on

 

I think I am going to buy a lighted scope and take some pictures when I put the bike up this winter and then compare them at the end of next year to see how big of a difference these systems make. I have had the same small filter on for 2 seasons so I will buy new for next year.

 

The K&N high flow AC I had on my FXDL was not externally vented. I had it on for about 1200 miles. When I removed it I didn't notice any oil residue inside. Maybe because it was not on that long.

Anyway, I think having the right level of oil in the engine has more to do with how much oil comes out of the breather than anything else. I will see what happens with this DK breather system I have now (same setup TinCup has).

 

Well IMO.. If it works. you are done.. I'd make sure the exit is pointing away from the tire but that's about it.. Doug Coffey of Headquarters like to run the lines up under the tank. Worked for him..

I'm not too hot on small catches.. If you have an issue with dribbling stuff, a small one won't hack it.. They might work if you don't have anything coming out of the breather but when what do you need it for then?? Another chrome Gooogaaa? When you start pushing these motors (both driving them hard and building them up). A small catch won't hack it and it'll blow crap.. The problems is that high compression forged pistons fit loose in the bore till they heat up.. During that time conventional rings will leak, allowing combustion gases into the crankcase.. Once hot all the water picks up oil on it's way out and you have a mess.