As others have said, there's no problem with leaving the safety out.
Like some other posters, I never actually use the QB78 safety. This is because I was taught to shoot by ex-British army veterans who had used bolt action rifles in combat. They drilled into me that if the bolt is open, the rifle is safe - and MUCH more obviously so than just setting the safety. As both Lee Enfield and QB78-family air rifles will not fire with the bolt open, even if the trigger is pulled a thousand times, the open bolt is always my guarantee of safety when shooting these air rifles, rather than a somewhat hard-to-see safety lever being rotated into position.
Archer Airguns Inc.
Online stores http://www.archerairguns.com