The RTF version comes with the low and high rates pre-set and I didn't see a specification anywhere in the manual. When I switched out the stock radio receiver for a Spektrum, I just gave each surface as much travel as it could handle. I ended up having to take a little elevator out of it but it flys great. You should be fine doing the same.

As for the CG, again they don't give a spec in the RTF manual that I could find. If you use the 1800 or 2200 mAh Parkzone lipo installed in the intended location, the CG should come out pretty close though.

Have you flown your T-28 yet? I've never really been a fan of foam or electric airplanes but this one impressed me enough to buy it. I've definitely enjoyed it so far.