The system is not perfect and can take a lot of experimentation to dial in properly. On top of all that, a lot of it is down to playing technique.
A trick I used to use with my old (even slower) 25-pin gear was to use a high-strung guitar (wound strings tuned an octave up) and then transpose patches on those strings down to normal octave. Worked pretty well, but means that you aren't getting a normal tuned guitar from your normal pickups. The GR-55 unfortunately does not let you tune on a per string basis, so you can't even do that anymore.