Given the number of transactions that happen in master, model and msdb on a daily basis, I have never found it necessary to move the logs of these three databases. Tempdb on the other hand can be moved with a dirty trick. Leave the existing log with a maxsize limit of say 5MB, and create a second logfile on the new device at the actual size you need. Logfiles are used in sequence, as opposed to datafiles which are used in a more distributed way. You will still have the original disk used for 5MB of logs every once in a while, but the vast majority of the usage should be on the other drive.