Beantownsbest If you are missing only 2 last letters from secret key you could try out all the combinations of letters and numbers. It would take some time but someone could write a little program for you that tries all combinations in 1 second. It would be a fun programming exercise.
Also, I think that the end of the secret key is used as a checksum (not 100% sure on this). This reduces the number of possibilities.
Just make sure your secret key starts with an S, so you know you are not missing the first 2.