Mounting a lathe spindle encoder

I have a lathe conversion I did on an Emco Maier Super 11 using AHHA!
drivers and software (Artisan). I am to the point where I need to mount the
spindle encoder to allow me to do CNC threading.

The Rotary Encoder AHHA! supplied looks to be well made and appears to have
ball bearings. It's a CUI Stack Inc. model # NSE-10-2MC-635 (.025" shaft ~
.500" long, body 1.5" diam, face mounted).

My understanding is that I need a 1:1 ratio between the encoder and the
spindle. I know I can achieve this by using a timing belt with the encoder
to one side but I'm worried about the side forces on the encoder shaft.
Should I be concerned about this (I assume I'd be using a fairly small light
belt so not a lot of tension would be needed)? How have others approached
this? My max spindle speed is 2,400 RPM.

Cheers,

Chuck Hackett
"Good judgment comes from experience, experience comes from bad judgment"
7.5" gauge Union Pacific Northern (4-8-4) 844
http://www.whitetrout.net/Chuck