If I were in your position I'd check the system and see if there is a port relief on both sides of the extend cylinder circuit. If there is there would definately be no problem using the cylinder if you set the port relief to 2500. By doing that it would pop before main relief did so that one cylinder would never see the full 2700 psi of system pressure.
Beyond that my only suggestion would be to call the cylinder mfg and ask them. Most all hydraulic components are designed with a safety factor enginered in to insure they don't rupture due to a pressure spike, etc. That said, 200 psi difference isn't that much so it might very well work just fine but given the dangers involved with high pressure oil I still wouldn't feel comfortable saying it would definately work without consulting the mfg.