You can get to it without removing the rail but its bloody fiddly to get to the two screws holding it on. Ive got to ask why you are bothering to change it though as the standard ones are perfectly fine for all but the most extreme set ups.
It's been running like a pig since running out of fuel I have changed the plugs and inline filter and also have ordered a sock filter for the pump as that is full of black shit so the fpr was next on the list if the filter dock isn't the issue I would only be replacing with std one anyway Thanks for your reply