Hello Matthew
Yes I keep the headjoint pulled out. Mr. Green recommends 3-4 mm for an alto but remember that's the way he tunes them. He only sends out that are in tune at 440 hz.
I compared prices on Amazon ($35) vs. Mr.Green ($55) for a Yamaha 300 alto. The extra $20 is well worth it for getting an instrument that is in tune and for the continued support he provides. You buy on-line and you have a recorder only. You buy from him and he will take time, email or on the phone, to answer any questions you have.
I got the Zen-On G-1A last year from David and it is almost as good as my Mollenhauer Rosewood alto. It has probably the most complex sound of any plastic recorder. The second octave is "bell-like" and (for me) very easy. This is my advice only. If you found the Antique Sound Workshop website read David's advice on plastic recorders, including his comments on the Aulos Haka. It is probably very much like the Zen-On in tone.
http://www.aswltd.com/guiderec.htm#plasticBest of luck...the recorder can be a very satisfying instrument to play. It is different from other woodwinds, lacking embouchure control, but it has advantages in it's simplicity at a basic level and it's complexity in alternate fingerings.
Frank