the upper frame box is basically serving as a oil catch tank. you can remove the hose from the intake boot and plug the bung and drop the hose into a breather filter (K&N type) to atmosphere,
mine is down and up front behind the skid plate. The the upper crankcase cover breather hose to its middle frame box barb, and lower to the oil pan drain plug for gravity scavanging of breather oil and vapor condensed oil.
Or just deal with breather oil loss and run the lower box hose down under the motor and install a standard TC oil plug down below doing away with the hose to the drain plug, that stuff is all emission stuff for crankcase vapor closed circuit set up. I would still leave the crankcase breather into the frame box and not directly to atmosphere with a breather filter for a little bit of closed air volume to deal with crankcase pressure pules, if I was doing this set up (completly eliminating the frame box as a catch tank).
I also found this but I am a little confused?