you should be able to get your fingers around the tailpipe in the outlet.. about an inch or 1.25 so it can draw air from the fuselage .

The way I solve the nose heavy is the following:
Pull the tank tray.. its held in by 6 glue points.
Make a tray UNDER the tank mount on the fuselage bottom.
Mount the fuel pump, smoke pump and Air trap under there. It will fit
Put the turbine battery on a tray right behind the tank, in front of, and even with the canopy. Put the ECU on the gear well..
Then put all your radio gear on the back of the tray.
I run all the air lines in one piece up to the front tray. Then in the hole put the couplers.
This will allow you to put 2 batteries up in the nose where they belong, and might even need a touch of nose weight.
The elan should sit on its tail with an empty gas tank and a full trap..

The elan is quite different than the other boomers.. It flies much better towards the back end of the CG scale.. and lands easier with 45 degrees of flap and 3/8 inch crow.

This is from about 700 flights on 5 different boomers, from sprints to XL's

goose.