At prime focus with that GEM and OTA , necessary .... no escaping the need.
You might get away without a guidescope for widefield stuff with that GEM for shorter fl lenses (to 200mm say ??) .
The PE of that GEM is not so flash from what I have read, depends on the pixcel scale on the image , if it is less than your GEM's PE and guiding errors for a given lens your are fine ,. otherwize .... you must guide.
http://www.eskimo.com/~rachford/widefield/calc.html
http://www.eskimo.com/~rachford/widefield/calc.html
and very handy
http://www.astro-imaging.com/Tutorial/Calculations.html
ie at prime focus , my 10" f4.66 has an image scale of 1.0 arcsec/pixcel for a chip with 5,6x5,6µm pixcels.
a 200mm lens has an image scale of 5.8 arcsec / pixcel , if the periodic error and drift is less than about 2x the calc pixcel resolution you wont need to guide.