carb drip tray

You don't want fuel that might come out of your carb overflows to drip on your exhaust. That could ignite.

I have a 912ul mounted on a RANS S-12 that has a pusher propeller. I bought it used. The engine is a very early model and either they didn't have the drip pan then or previous owners discarded it. In order to make sure the carb overflow would not have the potential to drip on the exhaust or anywhere over the engine or fuselage, I installed long tubes attached to the overflows that exit at the bottom and rear of the fuselage under the tail tube.

You might consider something like that for your installation.

In addition to catching/diverting carb drips, the carb drip pans also serve to insulate the carbs from the heat of the nearby exhaust pipes.

Many, many of us with the 912uls without airbox do not have the carb drip trays. We run the overflow tubes away from the exhaust.

Contrary to the common belief that the tubes are "OVERFLOW" Tubes, they are actually Float bowl "VENT" Tubes and are listed in the Parts Catalog as "AIR VENT LINEs".

Also, note that the Nipples that the lines attach to on the Carbs are ABOVE the Carb Throats.

No fuel will exit these lines until the carb THROATS are completely full of fuel.

The word "FLOOD" would be a gross understatement.

In the event of a stuck float valve, the fuel will overflow the float chambers and leak out the Idle and Main jets into the carb throats.

The purpose of the drip pans is to catch the fuel as it drips out of the carb THROATS.

The purpose of the VENT lines is to equalize the pressure in the float chambers to match the pressure at the mouth of the Carb Throats.

Running the lines outside of the cowls defeats their purpose and will cause the engine to run with an improper mixture and possibly a mixture that varies with airspeed.

The ends of these lines should be located very near the surface of the Air filters, or better yet a fitting should be attached to the air filters to allow the float chambers to be at the same pressure as the interior of the air filters preventing the engine from running Richer as the filters become more restricted over time.

Further to Bill's point, we created a video on this subject a while back:  https://www.rotax-owner.com/videos-topmenu/rotax-minute/454-carb-vent-lines