Why do you design a hydraulic cylinder? There are so many possibilities to buy it from a specialist and avoid all problems you shall be confronted with since if you put such a question you are not aware of the design specifics.
The tolerance depends on several factors as pressure, kind of seal, kind of antifriction ring, type of ram (single acting, double acting, with rod or without and so on ...) so better avoid troubles and buy it it will cost you less!