As Marilyn said, there is currently no way to save SHSH for 5.1, but once TinyUmbrella is updated, yes, you will be able to save 5.1 SHSH even if you aren't currently on that firmware. What TinyUmbrella does, is it generates and saves your SHSH for whatever the currently signed firmware is based off your device's ECID, so even if you were on iOS4 still, you would still be able to save your SHSH for the most current firmware since your ECID never changes.