oil residue

Time to go back on your basics and be sure you have a notch in the vent line as per the installation manual.  Without it you will always be getting some oil residue being drawn from the oil tank.  One other thing to check would be your crankcase pressure.  (also found in the installation manual) If you have high crankcase pressure it may be pushing too hard on the return to the oil tank and causing some oil mist to be pushed out.  The test  and the pressures are found in installation.  

Cheers

Food for thought:

Make sure this oil residue is actually coming from the oil tank vent hose.

I have one in the shop right now that the owner swore an oil leak was coming from the back of the engine. He said it was all over the firewall and under the planes belly. Where it was really coming from was the crankcase locking pin bolt hole. Someone didn't put the crush washer back in place and the wind through the cowl blew it to the back.

I've seen many with a very small amount of vapors from the tank vent tube. When you're up to operating temp in flight then contaminants are being cooked off into vapors. These have to go someplace. If your tube is hanging out in the air stream that may cause a low pressure area at the tube mouth and cause a little more suction at that point.

Most planes I see have some residue on the under belly from exhaust and vapors. Just wipe them off occasionally. 

Ok guys, here is a photo. The oil comes from the overpressure line.  This was after a 90 minute flight.  Everytime regardless of the fill level.  

The question at hand is do you think the small holding tank with an adequate hole in the cap to allow airflow will help solve the mess?

Yes I have a small hole in the line to break the vacumn from the airflow accross the body.  I have tried the line close to the body and further out with no change.  

The issue may be your tank won't vent the air passing through fast enough causing a back pressure. Part of the issue is your vent tube is out in the air stream. Some oil vapors are fairly normal on the belly. Part of the care and maint. of the aircraft is keeping it clean. Just wipe it off. I highly recommend a water based biodegradable cleaner called Oil Eater. No nasty solvents and as soon as you spray it on the oil runs off. I have been using it for over 20 years on all surfaces and never an issue. My wife even uses it on the stove hood for the grease that gets on there from cooking. I use it on my hangar floors for oil and fluids spilled. It won't hurt metal, carbon fiber or fiberglass.

Heath,

since you are sure that oil comes out from the bypass just try out if the additional "collector" helps. It seems more than worth trying and it is not a major change to the engine anyway. Costs are low, effort is limited, go for it.  Sounds like a solution to me. In case it does not help and you want to get rid of the engine I'll take it off you, and won't charge you ;-)