Hold it neutral and 'feel' for wind effects. If tailwind is stronger than the propwash, the elevator will tend to be blow to full up or full down, and you'll have to hold it positively neutral. If Propwash greater than tailwaind, elevator will tend to trail just below neutral (depending on weight bias of the system in no-wind conditions, and assuming you don't have one of those horrid spring-bias elevator 'trims' (Tiger Moth??) which just hides from your hands what is really going on back there).
As you vary the power and position relative to the wind as you taxy, you might find you have to sometimes let it trail and sometimes hold it positively neutral.
Someting to be aware of in the Chipmunk in a strong tailwind is the rudder. If you have a notch or two of brake set and you get a sudden strong gust from behind, if you're not bracing the rudder with your feet, it can get blown to full deflection, thus applying one wheel brake sharply, and lifting the tail - ideal conditions for a nose-over.
SSD