Generally it's best to avoid spacers if you can as they both add mass and also may disturb the fit with the headshell. I'd only use one if needed to ensure optimal SRA if the arm post is high relative to the headshell. Certainly adding one simply to use a stylus guard would seem odd. The Lyra guard is at least well designed with clear slots for fitting but with any guard you risk damaging the cantilever if you are clumsy putting it on or off. I do without, but my deck is in a dedicated room and no one else is cleaning or anything around it. So at the end of the day yes there may be a small sound quality loss but if it gives you peace of mind ....... of course you could instead get a different headshell, perhaps one of these 😉 which would work really well!