Q: polyA tail length vs. mRNA capture

[Steven Sullivan]

the length of polyA tails on various mRNAs is known to change in both 
directions during early development in many organisms.  This raises two 
similar questions pertinent to my research:

1) anyone know what the *shortest* length of polyA is that gets captured on 
oligo dT columns or hybridized to oligodT primers (e.g. LTI's oligo dT12-18)?


2) does reverse transcription pick up mRNAs with short polyA tails (and 
if so how short)?