(ET) Using Alltrax in E20

["CleanPower" <cleanpower att net>]

 Hi
With an eye toward installing an Alltrax controller I have the following 
question:
 From what I see in the Alltrax schematic,reverse rotation is obtained by 
reversing the field current. While this was commonplace practice on the 
EARLY E15 , The E20 always reversed the armature current to obtain reverse 
rotation. To those of you who have installed them in an E20: Is it working 
OK to reverse the field current?

 Thank You,
Harold Z.