I would recommend getting a proper lefty EUB as opposed to converting. However, I have done both - I converted a cheap HB from righty to lefty (flipped the bridge upside down, filed the bridge grooves so the strings sit correctly, filed the nut, reversed the spacing bracket, etc.) and then I also bought a lefty 5-string upright (NS NXT5). Converting a righty isn't hard, but the job needs to be done properly or you will hit some niggles deriving from the work - strings buzzing, dodgy action, etc. Having a professional do the work will obviously help, but also add to the total cost.