If you want the fly a bit heavier, use a thicker hook. In this picture the fly is tied on a Hanak H300 and the heavier hook is the Hanak H310.
Tie in a marabou tail as shown, I always mix three shades to give a more natural look.
Advance the threasd to behind the eyes and wind the remaining marabou forward. Secure it and trim.
Tie in a mixed bunch of marabou 'charlie' style after turning the fly over. They should protrude just beyond the hook bend, not the length of the tail.
Its easier to do two smaller bunches, but avoid excess thread build up.
Trim the marabou, whip finish and your fly is done.
Instructions for mounting the Veniard twin-eye
Put on a base layer of thread then move it back up the eye, and then back a bit.
Repeat this until the twin-eye fits on snugly. If the twin-eye doesn't go over the hook eye, then turn it 90 degrees as shown above.
Once you have it fitting snugly, take it off, put a generous amount of superglue onto the thread. (generous enough to soak through the thread and glue on the eye, not so much it drips) Put the eye back on over the glued portion, and continue with your fly.